Compound Interest Calculator
See how your savings or investments grow over time with compound interest and regular contributions.
How compound interest works
Compound interest is interest earned on both your original balance and on interest you've already earned. The more often it compounds — daily, monthly, or annually — the faster your balance grows, especially over long time horizons.
Why regular contributions matter
Adding a fixed amount on a regular schedule (like a monthly deposit) compounds alongside your starting balance. Over 20–30 years, consistent contributions are often the biggest driver of the final total — more than the starting amount itself.
Frequently asked questions
What's a realistic interest rate to use?
It depends on where the money sits. A savings account might earn 1–5%; a diversified stock portfolio has historically averaged roughly 7–10% a year over long periods — but that's not guaranteed, and any given year can be negative.
Does this account for taxes on the interest earned?
No, the result shown is gross growth before any taxes on interest, dividends, or capital gains. What you actually keep depends on the account type (taxable vs. tax-advantaged) and your local tax rules.
What's the difference between compound and simple interest?
Simple interest is earned only on the original principal. Compound interest is earned on the principal plus all interest already accumulated, which is why balances grow faster the longer they compound.
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