Compound Interest Calculator
See how a starting amount grows when interest is added to the balance and then earns interest itself. Enter the principal, the annual rate, how often interest compounds and for how long.
Uses A = P(1 + r/n)nt: P is the principal, r the annual rate as a decimal, n the number of times interest is added per year and t the time in years. No further deposits or withdrawals are assumed.
- Final amount
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- Principal
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- Total interest
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- Effective annual rate
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An estimate for learning and planning, not financial advice. Real accounts may differ because of fees, taxes, rate changes and how the provider rounds interest.
How to Use the Compound Interest Calculator
- Enter the principal, the amount you start with.
- Enter the annual interest rate as a percentage, for example 5 for 5%.
- Choose how often interest compounds: annually, semi-annually, quarterly, monthly or daily.
- Enter the time period and choose years or months.
- Read the final amount, total interest earned and effective annual rate, then copy or save the summary.
Examples
Savings compounded monthly
- Input
- Principal 10,000 · Rate 5% · Monthly · 10 years
- Output
- Final amount: 16,470.09 Total interest earned: 6,470.09 Effective annual rate: 5.1162%
Compounded once a year
- Input
- Principal 5,000 · Rate 4% · Annually · 3 years
- Output
- Final amount: 5,624.32 Total interest earned: 624.32
About the Compound Interest Calculator
Compound interest is interest calculated on both the original amount and the interest already added. Because each period’s interest becomes part of the balance, growth speeds up over time. It applies to savings accounts, certificates of deposit and reinvested returns, and it also explains how unpaid debt can grow.
The calculator uses the standard formula A = P(1 + r/n)^(nt). P is the principal, r is the annual rate as a decimal (5% = 0.05), n is the number of compounding periods per year (1, 2, 4, 12 or 365) and t is the time in years; months are divided by 12. Total interest is A − P. The effective annual rate, (1 + r/n)^n − 1, shows the yearly growth once compounding is included, which is why 5% compounded monthly works out to about 5.12% a year.
The result assumes a fixed rate, no deposits or withdrawals and no fees or taxes. Real accounts may also round interest differently or use a 360-day year, so treat the figures as an estimate for learning and planning, not financial advice. The calculation runs in your browser with JavaScript, and this tool does not send what you enter to a Usevanta server.
Frequently Asked Questions
What is the compound interest formula?
A = P(1 + r/n)^(nt), where P is the principal, r the annual rate as a decimal, n how many times interest is added per year and t the number of years. The interest earned is A − P.
Does compounding more often make a big difference?
It helps, but less than you might expect. 10,000 at 5% for 10 years grows to 16,288.95 with annual compounding, 16,470.09 with monthly compounding and 16,486.65 with daily compounding.
What is the difference between simple and compound interest?
Simple interest is paid only on the original principal, so it grows by the same amount each year. Compound interest is also paid on interest already earned, so the yearly gain gets larger over time.
Can I include monthly contributions?
Not at the moment. This calculator shows the growth of a single starting amount with no extra deposits or withdrawals.
What happens with a 0% interest rate?
The final amount equals the principal and the interest earned is 0, whatever the compounding frequency.
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