Compound Interest Calculator
Estimate how an initial investment grows over time with compound interest — with an optional recurring contribution added on top.
Added at the end of every compounding period (matches the frequency above).
$18193.97
Future value
$10000.00
Total contributions
$8193.97
Interest earned
This is an estimate that assumes a constant rate of return, which real investments rarely deliver year to year. It is not investment advice or a promise of returns.
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How to use compound interest calculator
- 1Enter your initial investment amount.
- 2Enter the annual interest rate and how many years you plan to invest.
- 3Choose how often interest compounds — annually, monthly, daily and more.
- 4Optionally add a recurring contribution per compounding period.
About this tool
Compound interest means interest is calculated not just on your original principal, but on the principal plus all interest already earned — so growth accelerates over time rather than staying flat, unlike simple interest. The more frequently interest compounds (daily versus annually, for example), the faster that acceleration happens, though the difference shrinks at realistic rates.
This calculator applies the standard compound growth formula period by period, adding any recurring contribution you specify at the end of each compounding period before the next round of interest is calculated — so your contributions also earn compound interest, not just your starting balance.
The result assumes a constant rate of return for the entire duration, which real investments essentially never deliver — markets and interest rates both fluctuate. Treat this as an illustration of how compounding works, not a forecast or a promise of investment returns.
Frequently asked questions
They use the same underlying compound growth math. This calculator frames the recurring amount as an optional add-on to a lump-sum investment, while the Savings Calculator puts regular contributions front and center — useful if you're building a balance from contributions rather than growing an existing lump sum.
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