Compound interest calculator
Enter a starting amount, a regular deposit and a rate to see what your savings could become, year by year.
Sealed on this device
Runs in your browser. Nothing is uploaded.
Sealed
Your savings plan
Leave empty or 0 if you won’t add money along the way.
Result
- Final balance
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- Total deposited
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- Total interest earned
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- Share of the balance that is interest
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- Effective annual rate
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How it’s calculated
Fill in the plan to see the result.
Without deposits, the starting amount follows P × (1 + r/n)^(n × t).
Growth over time
Bar chart of the balance at the end of each year, split between money deposited and interest earned. Use the left and right arrow keys to read each year. The full table follows.
Year by year
| Year | Deposited this year | Interest this year | Total interest | Balance |
|---|
How it works
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Describe your plan
Enter what you start with, what you add each month or year, the interest rate and how long you will save.
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Match your account
Choose how often interest is compounded and whether deposits arrive at the start or the end of each period, as stated by your bank.
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Read the growth
The chart and the yearly table show how much comes from your deposits and how much from interest. Copy the table to a spreadsheet if you like.
Frequently asked questions
What is compound interest?
It is interest earned on interest. Each period, the interest is added to your balance, so the next period’s interest is calculated on a larger amount. Over long periods, this makes savings grow faster and faster.
What is the compound interest formula?
For a single deposit, the final amount is A = P × (1 + r/n)^(n × t), where P is the starting amount, r the annual rate as a decimal, n the number of compounding periods per year and t the number of years. For 1,000 at 5 % compounded yearly over 10 years, that gives about 1,628.89.
Does compounding more often make a big difference?
A little. At 5 % a year, monthly compounding gives an effective rate of about 5.12 %, and daily compounding about 5.13 %. The rate itself and the time you stay invested matter far more.
How are regular deposits handled?
Each deposit starts earning interest from the month it is made. Deposits at the start of a period earn one more period of interest than deposits at the end, so they grow slightly more.
Are taxes, fees and inflation included?
No. The result is a projection at a constant rate, before taxes, fees and inflation. Real returns vary, especially for investments whose value goes up and down.
Is my financial information stored?
No. The calculation runs in your browser and your figures are never sent anywhere. Only your currency choice is remembered on this device.