Finance Calculator
Compound Interest Calculator
Estimate how your money could grow with compound interest. Enter a starting amount, interest rate, time period and optional regular contributions to see your estimated future balance and total interest earned.
- Estimate future value
- See interest earned
- Add regular contributions
Free to use · No sign-up required
Compound Interest Calculator
Calculate Compound Interest
Enter your starting balance, interest rate and time period to estimate how compound interest could grow your money. Add regular contributions to see their potential effect on your future balance.
Your Growth Details
Adjust the values below to model your savings or investment growth.
Estimated Growth
Your estimated result based on the values entered.
Future Balance Breakdown
This is a simplified estimate. It assumes a constant annual interest rate and reinvestment of interest. Taxes, fees, inflation and changes in the rate are not automatically included.
Calculation Method
How Compound Interest Is Calculated
Compound interest means interest is added to your balance at each compounding date. Once credited, that interest becomes part of the balance and can itself contribute to future interest growth.
Standard Compound Interest Formula
Future value after the starting balance has compounded for the selected period.
Starting principal — the amount initially deposited or invested.
Nominal annual interest rate expressed as a decimal. For example, 6% becomes 0.06.
Compounding periods per year, such as 12 for monthly or 4 for quarterly compounding.
Time in years that the balance is allowed to grow.
How Regular Contributions Are Handled
- 1 The calculation begins with your starting balance.
- 2 Between calculation events, interest accrues on the current balance using the nominal annual rate on a pro-rata basis.
- 3 Accrued interest is added to the balance on each scheduled compounding date. Once credited, it becomes part of the balance used for later interest calculations.
- 4 Regular contributions are added at the end of each selected contribution period. If a contribution and a compounding event occur at the same time, compounding is applied first.
- 5 The process continues until the end of the selected term, producing the estimated future balance, total contributions and total interest earned.
For example, you can calculate monthly compounding with weekly contributions, or quarterly compounding with monthly contributions. The calculator keeps these two schedules separate when estimating growth.
$10,000 at 6% for 10 Years
This first example isolates the starting balance so you can see the standard compound-interest formula without regular contributions.
Why Regular Contributions Need a Separate Calculation
The standard formula above is straightforward when calculating growth on a single starting amount. This calculator can also use monthly, fortnightly, weekly, quarterly or annual contributions independently of the selected compounding frequency. It therefore processes compounding dates and contribution dates separately. When the contribution frequency and compounding frequency are the same, the calculation is consistent with the standard future-value approach for end-of-period contributions. Actual savings or investment results may differ because of provider interest-crediting methods, day-count conventions, fees, taxes, rate changes and other conditions.
Understanding Your Results
What Your Compound Interest Results Mean
Your result shows more than just the amount your money could grow to. It separates the money you put in from the estimated interest generated over time, helping you see where your future balance comes from.
Estimated Future Balance
This is the estimated amount you could have at the end of the selected time period. It combines your starting amount, regular contributions and estimated interest earned.
Starting Amount
This is the initial amount you entered into the calculator. It forms the original principal that begins earning interest from the start of the calculation.
Total Contributions
This is the total amount of regular contributions added during the selected term. It does not include your starting amount or interest earned.
Total Interest Earned
This is the estimated growth produced by interest after subtracting your starting amount and regular contributions from the final balance. As credited interest becomes part of the balance, it can contribute to future compound growth.
Where Does Your Future Balance Come From?
The calculator separates your estimated future balance into three components. This makes it easier to distinguish the money you supplied from the growth generated by compound interest.
Reading the Balance Breakdown
The calculator’s balance bar shows what percentage of your estimated final balance comes from your starting amount, subsequent contributions and interest.
What to Look For
Try changing one input at a time and compare how the estimated balance responds.
- A longer time period gives existing interest more opportunity to participate in later compound growth.
- A higher assumed interest rate can substantially increase the estimated future balance over a long period.
- Regular contributions increase the amount of your own money in the balance and can also create additional opportunities for future interest growth.
Compound Growth Can Become More Noticeable Over Time
Early in a long-term calculation, much of the balance may still consist of the money you contributed. As credited interest accumulates and becomes part of the balance, later interest can be calculated on a larger amount. This is why time can have a substantial effect on compound-growth estimates. The calculator assumes the entered rate continues for the full term, so the result should be treated as an estimate rather than a guaranteed return.
Compound Interest Examples
See How Compound Growth Changes Over Time
Compound growth can change significantly when you adjust the time period, interest rate or regular contribution. These examples show how each factor can affect the estimated result.
What Happens When Money Has More Time to Compound?
Start with $10,000 at a 6% annual interest rate, compounded monthly, with no additional contributions. Only the length of time changes.
Why the Later Years Matter
The balance does not grow by the same dollar amount every year. As previously credited interest becomes part of the balance, there is more money available to earn interest in later periods. In this example, the original $10,000 grows to more than $60,000 after 30 years if the 6% rate remains unchanged.
How Much Difference Can the Interest Rate Make?
Now keep the starting amount and 10-year term the same, but compare three different annual rates. Each example uses monthly compounding and no additional contributions.
Small Rate Differences Can Become Significant
Over 10 years, the estimated balance is about $13,493.54 at 3%, $18,193.97 at 6% and $24,513.57 at 9%. Because the rate affects each compounding period, its impact can become increasingly noticeable over longer time horizons.
What If You Add $100 Every Month?
Compare the same $10,000 starting balance at 6% for 10 years with and without a $100 contribution at the end of every month.
No Regular Contributions
$100 Every Month
End of each monthContributions Can Affect Both Principal and Growth
Adding $100 per month contributes $12,000 of additional money over 10 years. Because each contribution can also participate in later compound growth, the estimated future balance rises to approximately $34,581.90 rather than simply adding $12,000 to the no-contribution result.
Example assumptions: Figures are rounded to the nearest cent and assume the stated nominal annual rate remains constant for the full term. Monthly contributions are made at the end of each month. These examples do not include taxes, fees, inflation or changing interest rates and are provided for illustration only.
Compounding Frequency
How Compounding Frequency Affects Growth
Compounding frequency describes how often accumulated interest is added to the balance. With the same nominal annual rate, more frequent compounding can produce a slightly higher future balance because credited interest begins participating in future growth sooner.
The Annual Rate Is Divided Across Compounding Periods
With a nominal annual rate of 6%, annual compounding applies 6% once per year. Monthly compounding divides the nominal rate into 12 periods, giving a periodic rate of 0.5% per month.
Once interest is credited, it becomes part of the balance. The next compounding period can therefore calculate interest on both the original principal and previously credited interest.
More Frequent Does Not Mean Proportionally More Growth
More frequent compounding means interest is credited more often.
But the nominal annual rate is divided into smaller periodic rates.
As compounding becomes increasingly frequent, the additional benefit from each further increase in frequency generally becomes smaller.
$10,000 at 6% for 10 Years
The starting amount, nominal annual rate and time period stay exactly the same. Only the compounding frequency changes. No regular contributions are included.
Annual vs Daily Compounding
In this example, changing from annual to daily compounding increases the estimated 10-year balance by about $311.81. The compounding frequency matters, but the starting amount, interest rate and length of time can have a much larger influence on long-term results.
Compare Rates on the Same Basis
Compounding frequency is only one part of comparing savings or investment growth. A quoted nominal annual rate and an effective annual rate are not necessarily the same measure. When comparing financial products, check how the provider states the rate, how often interest is calculated and credited, and whether fees, taxes, minimum balances or other conditions apply.
Regular Contributions
How Regular Contributions Can Build Your Balance
Compound growth does not have to begin and end with one starting deposit. Adding money regularly increases the amount in your balance, and earlier contributions have more time to participate in future compound growth.
Contributions Add More Than Their Face Value
Every regular contribution directly increases the amount in your account or calculation. Once that money has been added, it can also participate in later interest calculations.
This means the estimated effect of a contribution can include both the money contributed and any subsequent interest generated while that money remains in the balance.
When Are Contributions Added?
This calculator assumes each regular contribution is made at the end of its selected contribution period.
Interest accrues on the current balance between calculation events.
Accrued interest is credited on each scheduled compounding date.
A contribution is added at the end of its contribution period.
If a compounding date and contribution date coincide, the calculator credits the accrued interest first and then adds the contribution.
Choose How Often Contributions Are Added
Contribution frequency is separate from compounding frequency. For example, you can model weekly contributions while interest compounds monthly.
$100 Per Month for 10 Years
Start with $10,000, add $100 at the end of every month and assume a 6% nominal annual rate compounded monthly for 10 years.
Earlier Contributions Have More Time
A contribution made near the beginning of the calculation can remain in the balance for much longer than one made near the end. As a result, earlier contributions generally have more opportunities to participate in subsequent compound growth when the interest rate is positive.
Contribution Frequency Changes the Cash Added
The contribution amount is applied every time the selected contribution period ends. For example, $100 monthly means $1,200 is contributed over a full year, while $100 weekly means 52 separate $100 contributions over a full year.
Contribution Frequency and Compounding Frequency Are Separate
Do not assume that choosing weekly contributions means interest also compounds weekly. The calculator treats the two schedules independently. Use the compounding frequency that matches the interest arrangement you want to model, then separately choose how often money is contributed. The results are estimates and do not account automatically for fees, taxes, inflation or changing interest rates.
Growth Factors
Factors That Affect Compound Growth
Compound growth depends on more than one number. Your starting balance, interest rate, time period, compounding frequency and regular contributions can all influence the estimated future balance.
Starting Amount
A larger starting principal gives the calculation a larger balance from which interest can begin accruing. With the other inputs unchanged, a higher starting amount generally produces more interest in dollar terms.
Changes the initial baseAnnual Interest Rate
The annual rate determines how quickly interest accrues. Over longer periods, even a relatively small difference in the assumed rate can produce a substantial difference in the estimated future balance.
Changes the growth rateTime
Time gives credited interest more opportunities to become part of the balance and contribute to later growth. This is why extending the term can have a powerful effect on a compound-interest estimate.
Adds more growth periodsCompounding Frequency
Compounding frequency determines how often accrued interest is credited to the balance. With the same nominal annual rate, more frequent compounding can result in a slightly higher future value.
Changes interest-crediting timingContribution Amount
Regular contributions increase the amount of money in the balance. Once added, those contributions can also participate in later interest calculations for the remainder of the selected term.
Adds new money over timeContribution Frequency
The selected frequency determines how often the entered contribution amount is added. For example, $100 monthly and $100 weekly are different contribution plans and result in different total amounts being contributed.
Changes amount and timingCompound Growth Comes From Several Inputs Working Together
No single input tells the whole story. The final estimate reflects the interaction between the balance, rate, time, compounding schedule and any contributions you choose to add.
Rate × Time
The effect of an interest rate becomes more pronounced when it is applied over a longer period. A rate difference that appears modest over one year can produce a much larger difference over decades.
Contributions × Time
Contributions made earlier generally have longer to participate in subsequent interest growth. Later contributions have less time remaining before the end of the calculation.
Rate × Compounding
Compounding frequency affects when accumulated interest is credited. At the same nominal annual rate, more frequent crediting can increase the effective growth over a full year.
Real-World Results Can Be Different
The calculator provides a mathematical estimate using the values you enter. Actual savings or investment outcomes can be affected by additional factors that are not automatically included in the calculation.
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Changing Interest Rates
The calculator assumes the entered annual rate remains constant. In practice, savings rates and other rates of return can change over time.
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Fees and Charges
Account, platform, management or transaction fees can reduce the amount remaining to compound.
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Taxes
Depending on your country, account type and circumstances, tax may reduce the amount of interest or investment growth you ultimately retain.
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Inflation
A future balance may be larger in nominal terms, but inflation can reduce what that money is able to buy in the future.
See Which Inputs Make the Biggest Difference
Change one input at a time in the calculator to see how the starting amount, rate, term, compounding frequency and contributions affect your estimated future balance.
Assumptions & Limitations
What This Compound Interest Calculator Assumes
The calculator provides a mathematical estimate based on the values you enter. Understanding its assumptions helps you interpret the result correctly and recognise why an actual account, savings product or investment may produce a different outcome.
Constant Annual Interest Rate
The annual interest rate you enter is assumed to remain unchanged for the entire calculation period. The calculator does not automatically model future rate increases or decreases.
Interest Remains in the Balance
Interest credited at a compounding date is assumed to remain in the balance. It can therefore participate in subsequent interest calculations rather than being withdrawn.
Contributions Stay Constant
If you enter a regular contribution, the calculator assumes the same amount is contributed at every selected contribution interval for the full term.
Contributions Are Made at Period End
Regular contributions are assumed to be added at the end of each selected contribution period. A beginning-of-period contribution model would produce a different result when the interest rate is positive.
Frequencies Are Treated Separately
Compounding frequency and contribution frequency do not have to match. The calculator keeps the two schedules separate, allowing combinations such as monthly compounding with weekly contributions.
The Entered Rate Is a Nominal Annual Rate
The annual rate is treated as a nominal annual rate for the selected compounding schedule. It should not automatically be interpreted as an effective annual rate.
What the Calculator Does Not Model
The calculator intentionally focuses on compound-interest mathematics. The following real-world factors are not automatically deducted from or applied to your result.
Fees and Charges
Account fees, management fees, platform charges, transaction costs and other expenses are not automatically deducted.
Taxes
The calculator does not estimate income tax, withholding tax, capital gains tax or other jurisdiction-specific tax consequences.
Inflation
Results are shown in nominal currency amounts. The calculator does not adjust the future balance for changes in purchasing power.
Variable or Negative Returns
The calculator applies the positive annual rate you enter as a constant rate. It does not simulate fluctuating market returns, losses or investment volatility.
Withdrawals
There is no separate withdrawal schedule. Money removed from an actual account would reduce the balance available for subsequent growth.
Provider-Specific Rules
Minimum balances, tiered rates, promotional rates, eligibility rules and provider-specific interest-crediting conventions are not modelled.
How the Calculator Processes Events
When contribution and compounding frequencies differ, the calculator processes them as separate events over the selected time period. This allows a contribution schedule to operate independently from the interest compounding schedule.
Interest accrues on the current balance between events using the entered nominal annual rate.
Accrued interest is added to the balance on a scheduled compounding date and at the end of the calculation where applicable.
Contributions are added at the end of each selected contribution period.
When a contribution and compounding event occur at the same time, the calculator credits accrued interest first and then adds the contribution.
An Estimate Is Not a Guaranteed Future Balance
The result shows what would happen mathematically if the values and assumptions entered into the calculator applied throughout the selected period. Actual outcomes may be higher or lower because rates, contributions, fees, taxes, inflation and other real-world conditions can change.
Important: This calculator is provided for general informational and educational purposes only. It does not provide financial, investment, tax or legal advice and should not be treated as a prediction or guarantee of future performance. Consider the terms of the relevant financial product and, where appropriate, seek advice from a qualified professional.
Calculate Your Growth
See What Compound Interest Could Do Over Time
Enter your starting amount, interest rate and time period, then test different compounding frequencies and regular contributions to see how they change your estimated future balance.
Free to use · No sign-up required · Results are estimates
Frequently Asked Questions
Compound Interest Calculator FAQs
Find answers to common questions about compound interest, compounding frequency, regular contributions and how to interpret the calculator’s results.
What is compound interest?
Compound interest is interest calculated on a balance that can include both the original principal and interest credited during earlier compounding periods. Once interest is added to the balance, it can contribute to future interest calculations.
How is compound interest calculated?
For a single starting amount with no regular contributions, the standard formula is A = P × (1 + r ÷ n)^(nt), where A is the future value, P is the starting principal, r is the nominal annual interest rate expressed as a decimal, n is the number of compounding periods per year and t is the time in years.
What does compounding frequency mean?
Compounding frequency describes how often accrued interest is credited to the balance. This calculator lets you model annual, semi-annual, quarterly, monthly or daily compounding. With the same nominal annual rate, more frequent compounding can produce a slightly higher future balance.
Does daily compounding always produce more than monthly compounding?
With the same positive nominal annual rate, starting balance, time period and no other changes, daily compounding generally produces a slightly higher mathematical result than monthly compounding because interest is credited more frequently. The difference may be relatively small, particularly over shorter periods or at lower interest rates.
Can I include regular contributions?
Yes. You can enter a regular contribution and choose whether it is added weekly, fortnightly, monthly, quarterly or annually. The calculator assumes each contribution is made at the end of the selected contribution period.
Do my contribution frequency and compounding frequency have to match?
No. The calculator treats the two schedules separately. For example, you can model weekly contributions with monthly compounding or monthly contributions with quarterly compounding. If a contribution and compounding event occur at the same time, accrued interest is credited first and the contribution is then added.
What is the difference between total contributions and interest earned?
Total contributions is the sum of the regular amounts added during the selected term, excluding the original starting amount. Total interest earned is the estimated portion of the final balance remaining after subtracting the starting amount and total contributions.
Does the calculator account for inflation?
No. Results are shown as nominal currency amounts. The calculator does not automatically adjust the future balance for inflation or changes in purchasing power.
Are taxes and fees included in the result?
No. Taxes, account fees, management fees, transaction costs and other charges are not automatically included. These can reduce the amount you actually retain or the balance available for future compounding.
Is the compound interest calculator a prediction of future returns?
No. The calculator provides a mathematical estimate based on the values you enter and assumes the entered annual rate remains constant for the selected period. Actual results can differ because rates, returns, contributions, fees, taxes, inflation and other real-world conditions may change.
Use the Calculator for Estimates
Compound-interest calculations are useful for exploring scenarios, but they cannot guarantee a future financial outcome. For an actual savings account, investment or other financial product, check the provider’s rate, compounding method, fees, terms and conditions.
References & Sources
Sources Used for This Calculator
We use established financial education and consumer information sources to support the definitions, methodology and explanatory content used on this page.
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ASIC MoneysmartView Source
Compound Interest Calculator
Australian Government financial guidance covering compound interest, regular deposits, compounding frequency, calculator assumptions and the limitations of estimated results.
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Investor.gov · U.S. Securities and Exchange CommissionView Source
Compound Interest Calculator
Investor education resource demonstrating how an initial amount, regular contributions, time, interest rate and compounding frequency can be used to explore compound growth.
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Consumer Financial Protection BureauView Source
How Does Compound Interest Work?
Consumer education explanation of principal, interest rates, compounding frequency and earning interest on previously accumulated interest.
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Investor.gov · U.S. Securities and Exchange CommissionView Source
What Is Compound Interest?
Educational explanation of compound interest and how earning interest on accumulated interest can affect growth over longer periods.
Our Calculation Method
Everything Calculated uses standard compound-interest principles and clearly stated assumptions to produce its estimates. You can learn more about how we build, check and explain our calculators in our calculator methodology .
Source note: External sources are provided for reference and further reading. Financial products and provider calculation methods can differ, so always check the terms and calculation method that apply to the specific product you are evaluating.