Compound Interest Calculator

A compound interest calculator shows how savings or investments grow when you earn interest on your interest, not just on the original amount. You choose the principal, the annual rate, the number of years, and how often interest compounds — yearly, quarterly, monthly, or any whole number of times up to daily. Growth is a curve rather than a line, and most of the money arrives late: at 10% a year, ₹1,00,000 gains about ₹61,000 in its first five years and about ₹2,55,000 in the five years from year 15 to year 20. That is why time in the calculation is worth more than anything else in it. It all runs in your browser.

How to use it

1. Enter the principal, the annual interest rate, and the number of years.
2. Choose how many times a year interest compounds.
3. See the maturity amount and the total interest earned.
4. Change one input at a time — the rate, then the years, then the frequency — and watch which of the three actually moves the answer.

Examples

• ₹1,00,000 at 10% for 2 years, compounded yearly → ₹1,21,000.
• The same amount compounded monthly → about ₹1,22,039.
• Over 10 years, ₹1,00,000 at 10% reaches ₹2,59,374 compounded yearly and ₹2,71,791 compounded daily — the whole span from once a year to every day is about ₹12,400.
• Raise the rate to 11% instead and the same 10 years reach ₹2,83,942 — one extra point of rate beats every compounding frequency there is.

Frequently asked questions

What is the compound interest formula?

The formula is A = P × (1 + r ÷ n)^(n × t), where P is the principal, r is the annual rate as a decimal, n is how many times a year it compounds, and t is the number of years. The interest earned is A − P.

How is compound different from simple interest?

Simple interest is calculated only on the original principal, so it grows in a straight line. Compound interest is calculated on the principal plus all previously earned interest, so it accelerates over time. The longer the period, the bigger the gap.

Does compounding frequency matter?

Yes, but far less than people expect, and it is the input least worth agonising over. On ₹1,00,000 at 10% for 10 years, yearly compounding gives ₹2,59,374 and daily gives ₹2,71,791 — the entire range from once a year to every day is about ₹12,400. One extra percentage point of rate over the same period is worth ₹24,568, and one extra year is worth ₹25,937. Rate and time are the levers; frequency is the detail advertisements lean on because the other two are harder to improve.

How does FD compounding work in India?

Most Indian bank fixed deposits compound quarterly. Our FD calculator uses that convention specifically; this compound interest calculator lets you pick any frequency to model other products.

How long will it take to double my money?

Divide 72 by the interest rate and you have the answer in years, near enough. At 8% that predicts 9 years against an exact 9.01; at 12% it predicts 6 against an exact 6.12. The rule of 72 drifts at very high rates, but it is close enough for any rate a bank or a fund is likely to offer, and it works without a calculator. For the precise figure, enter the numbers here: ₹1,00,000 at 8% compounded yearly reaches ₹1,99,900 after 9 years.

Does this account for inflation or tax?

No. It shows the nominal amount — what the statement will say, not what the money will buy. A deposit earning 7% while prices rise 6% leaves you barely 1% better off in real terms, and interest is usually taxed on top of that. Run the same period through an inflation calculator to see the purchasing power, and subtract tax at your own slab, before deciding whether a rate is genuinely good.

Why does my bank's figure differ from this one?

Usually the frequency or the day count. Indian fixed deposits compound quarterly by convention, so a bank quoting 7% will not match this calculator left on yearly — our FD calculator uses quarterly for exactly that reason. Banks also work in exact days rather than whole years, apply the rate that was in force on the day you deposited, and deduct tax at source once interest passes the annual threshold. Match the frequency first; that closes most of the gap.