Compound Interest Calculator
Watch savings grow: initial deposit, monthly contributions, interest rate and time — compounding handled correctly.
Assumes monthly compounding and contributions at month-end. Taxes and inflation are not included.
Why compounding feels like magic
Compound interest pays interest on your interest: each month your balance grows, and the growth itself starts growing. The effect is non-linear — $100/month at 7% for 10 years is about $17,400, but at 20 years it is roughly $52,400, and at 30 years about $122,000. Time in the market does more work than the size of the deposit, which is why starting early beats starting big.
Frequently asked questions
What does “7% annual rate” really earn?
Nominal return is not guaranteed for stock-market investments — 7% is a common long-run historical average for broad index funds after inflation adjustments vary. Savings accounts pay less; the tool simply does the math for whatever rate you enter.
How is this different from the loan calculator?
Same math, opposite direction: the loan calculator works out the payment that amortises a debt to zero, while this projects a balance growing upward. Both use monthly compounding.