See how your savings grow with compound interest over time.
What is compound interest? Compound interest is interest earned on both your original money and the interest already added to it. Because growth builds on growth, money compounds faster over time — which is why starting to save early matters so much.
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Tip: calculate first — your result is included when you share.
📚 Related guide:Rule of 72: How Long to Double Your Money? — divide 72 by your annual rate for an instant doubling-time estimate, with worked examples and the reverse formula.
How to Use the Compound Interest Calculator
Compound interest is often called the eighth wonder of the world: you earn interest not only on your original money but on all the interest added before. Over years and decades, that snowball effect turns modest regular savings into serious wealth — which is why starting early beats investing more later.
Enter your initial investment, the expected annual interest rate, the number of years, and any monthly contribution, then press Calculate Growth. You'll see the projected future value, how much you personally put in, how much is pure interest, and a year-by-year growth table showing the snowball in action.
Two insights the table makes obvious: time matters more than timing — doubling the years roughly quadruples the interest at typical rates; and regular monthly contributions usually contribute more than the starting lump sum. Even small rate differences compound enormously over 20–30 years, so compare savings accounts and funds carefully.
A reality check: this calculator shows nominal growth before inflation and tax. At 3% inflation, money doubles in purchasing power only when it grows well above that rate — so treat the projection as a planning guide. To see the flip side (what borrowing costs you), try our EMI / Loan Calculator.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Each compounding period, your balance grows a little faster than the last.
What is the compound interest formula?
A = P(1 + r/n)^(nt), where P = principal, r = annual rate (decimal), n = compounds per year, t = years. With monthly contributions, the future value of those payments is added on top.
How often should interest compound?
More frequent compounding grows money slightly faster, but the difference between monthly and daily compounding is tiny. The rate and the time horizon matter far more.
What is the Rule of 72?
A quick mental trick: divide 72 by your annual interest rate to estimate how many years it takes money to double. At 8%, money doubles roughly every 9 years (72 ÷ 8).
Does this account for inflation and tax?
No — the projection is nominal (before inflation) and pre-tax. Subtract expected inflation (often ~2–3%) to estimate real purchasing power.
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