Compound Interest Calculator is a free tool that shows how savings grow when interest earns interest of its own. Enter a starting amount, a monthly deposit, an annual rate and the number of years. The maths runs in your browser and nothing is uploaded.
How to project savings growth
- Enter your Starting amount and the Monthly deposit you can keep up.
- Set an Annual rate as a realistic real return, then choose Years.
- Compare Future value against You put in to see what compounding added.
- Scan the yearly table: the interest column should overtake deposits in later years.
The $500-a-month example
Saving $500 a month for 20 years at 7% turns $120,000 of deposits (plus a $10,000 start) into roughly $260,000. Almost half is interest. Start ten years later and the same deposits reach only about $100,000 — time, not timing, does the heavy lifting.
Saving while borrowing?
Money kept in savings while carrying high-interest debt usually loses: a 20% credit-card rate destroys wealth faster than a 7% portfolio builds it. Price the debt first with the Loan Calculator, then project what the freed payment grows into here.
Frequently asked questions
How is compound growth calculated here?
Monthly compounding with contributions added at the end of each month. The rate is a fixed nominal APR, so real investments with fees and market swings will differ.
Why do small monthly deposits matter so much?
Because every deposit starts earning its own interest immediately. Over 20–30 years, regular contributions usually exceed the starting amount and most of the final interest comes from them.
What rate should I enter?
Use a real return after inflation for planning: savings accounts 1–4%, a mixed portfolio 5–7% long term. The tool shows the maths, not a prediction.
Does it include tax?
No. Interest, dividends and capital gains are taxed differently by country and account type, so treat the result as pre-tax growth.
Last updated