Compound Interest Calculator
Calculate compound interest growth with regular contributions, with an optional start date
Leave empty for plain year numbers. With a date, each row of the table shows the date its year ends, and the result shows the date of the final balance. The date only labels the timeline; the amounts do not change.
Contributed
$1,000.00
Interest Earned
$1,009.66
Final Balance
$2,009.66
Details
Balance = P(1 + r/n)^(n t) + contributions grown at the same rate, where P is the starting amount, r the annual rate, n the compounding periods per year and t the years. Your monthly contribution is spread across the periods and added at the end of each. Interest earned = final balance minus everything you put in. With inflation, today's money = final balance / (1 + inflation)^t. Taxes, fees and changing rates are not included.
Monthly contributions are spread across the compounding periods and added at the end of each one. Estimate only; not investment advice.
Reading results never uses a trial use. Copying, saving or printing uses 1 per visit.
About Compound Interest Calculator
Calculates how an investment or savings balance grows with compound interest from your starting amount, regular monthly contributions, interest rate, compounding frequency and time horizon, with a year-by-year table and the value in today's money.
Enter your starting amount, monthly contribution, annual rate and number of years, and pick how often interest compounds. Choose whether contributions are made at the start or the end of each period, and optionally an inflation rate to see the result in today's money. Add a start date to see the date each year ends and the date of the final balance; it only labels the timeline and never changes an amount.
More frequent compounding produces a slightly larger balance at the same stated rate, but the rate and the number of years matter far more. Starting earlier beats contributing more later.
Watch: Compound Interest Calculator in Action
- Does compounding frequency actually make a meaningful difference?
- Yes — more frequent compounding (monthly versus annually, for example) produces a slightly larger balance over long time horizons at the same stated rate. It's worth checking which compounding frequency your actual account uses.
- What does the start date do in the compound interest calculator?
- It is optional. Enter the day the money starts earning interest and each row of the year-by-year table shows the date its year ends, with the date of the final balance above it. Leave it empty and the table shows plain year numbers, as before.
- Does the start date change the interest earned?
- No. The date only labels the timeline. Interest is worked out from the rate, the compounding and the number of years you enter, so the balance is the same for any start date. If your term is not a whole number of months, the final date is rounded to the nearest month and the page says so.
- Can I choose whether contributions go in at the start or end of each period?
- Yes. Under Contributions made, pick At the end of each period or At the start of each period. Contributions at the start earn interest for one extra period, so the final balance is a little higher, and the Details text and the note under the result name whichever option is selected.
- Which compounding options can I pick?
- Annually, semi-annually, quarterly, monthly or daily.
- Which currencies does it support?
- USD, EUR, GBP, INR, CAD, AUD, JPY, SGD, AED and ZAR.
- How do I see the result in today's money?
- Enter an optional inflation rate. Today's money is the final balance divided by (1 + inflation) raised to the number of years.
- What is not included in the result?
- Taxes, fees and changing rates are not included. It is an estimate only, not investment advice.
- Does reading the result use a trial use?
- No. Reading results never uses a trial use. Copying, saving or printing uses 1 per visit. Professional tools like this one have 10 trial uses a day.
- Can I use this to plan 401(k) retirement savings?
- It shows general compound growth. For a 401(k) projection with employer match and the IRS contribution limit, use the 401(k) Calculator, the next step in the Planning for Retirement guide.
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