Compound Interest Calculator
This compound interest calculator shows how a single investment grows when its earnings start earning their own returns. Enter your starting amount, the annual rate, the number of years, and how often interest compounds — and watch the future value respond instantly. Compounding is the engine behind every savings account, fixed deposit, bond and long-term investment; this page lets you see exactly how powerful it is with your own numbers.
The lump sum you start with — savings, a deposit, or an investment you have already made.
The yearly growth rate. Savings accounts pay 3–6%; long-run stock-market returns have averaged 8–12%; Indian FDs pay 6–7.5%.
How long the money stays invested. Compounding needs time — the last years do most of the work.
How often interest is added: 1 = yearly, 4 = quarterly, 12 = monthly, 365 = daily. More frequent compounding earns slightly more.
Future value
Log in to save₹4,92,680
What your money grows to by the end — e.g. ₹1,00,000 at 8% monthly-compounded for 20 years becomes ₹4,92,680.
The growth compounding added on top of what you put in — money you didn't have to work for.
Your original stake, shown so you can compare it directly against the future value and interest earned.
How many times over your money grew — a multiple of 4.9 means every ₹1 became ₹4.90.
How to use this compound interest calculator
- 1Initial investment: the amount you are starting with today. If you also plan to add money monthly, use our SIP calculator instead — this one models a single lump sum.
- 2Annual rate: be realistic. Bank savings: 3–6%. Indian FDs: 6–7.5%. Long-run equity index returns: 8–12% before tax and inflation. Overestimating the rate is the most common planning mistake.
- 3Years: the magic variable. At 8%, money doubles roughly every 9 years — so the difference between 15 and 30 years is not 2× but 4×.
- 4Compounding frequency: yearly (1), quarterly (4), monthly (12) or daily (365). The effect is small but real — daily compounding at 8% beats yearly by about 0.3% per year.
Understanding your results
Future value is what your money becomes; total interest is what compounding added for free. The growth multiple is the most instructive number: ₹1,00,000 at 8% for 20 years becomes ₹4,92,680 — a 4.9× multiple — while the same money at 4% only reaches ₹2,22,258. Rate differences that feel trivial per year are enormous over decades. One honest caveat: this calculator shows nominal growth. Inflation of 3% turns an 8% nominal return into roughly 5% real, and taxes take a further bite unless the money is sheltered in a tax-free instrument like PPF or ELSS. Plan with the real, after-tax rate if you want the truth.
The formula
A = P × (1 + r/n)^(n×t)A is the final amount, P the principal, r the annual rate as a decimal, n the number of compounding periods per year, and t the years. Each period, interest is computed on the growing balance — that is the 'compound' part: interest earning interest. As n grows toward infinity the formula converges to continuous compounding, A = P·e^(rt), but the practical difference between daily and continuous compounding is negligible. The exponential in this formula is why growth looks slow for years and then explodes: doubling times are constant, so each doubling adds as much as all previous growth combined.
A worked example
₹1,00,000 invested at 8% compounded monthly for 20 years: monthly rate 0.667%, 240 periods, giving 1,00,000 × (1.006667)^240 ≈ ₹4,92,680. Interest earned: ₹3,92,680 — nearly four times the original stake, contributed by compounding alone. Break it into decades: after 10 years the balance is only ₹2,21,964; the second decade adds ₹2,70,716. That back-loaded shape is why starting at 25 instead of 35 matters more than any other investment decision. A ₹5,00,000 FD at 7% compounded quarterly for 10 years matures at ₹10,00,799 — exactly doubling, matching the Rule of 72 (72 ÷ 7 ≈ 10.3 years).
Things to know
In India, FD interest is taxed at your slab rate (a 7% FD returns under 5% post-tax in the 30% slab), while PPF compounds tax-free — often making PPF's lower headline rate the better real deal. EPF and tax-saving ELSS mutual funds offer similar tax-sheltered compounding. Whichever instrument you choose, compare rates after tax and after inflation: a 7% tax-free return beats a 9% fully-taxed one for most higher-rate payers.
Frequently asked questions
How do I calculate compound interest?+
Use A = P(1 + r/n)^(nt): principal times (1 + rate per period) to the power of total periods. For ₹1,00,000 at 8% monthly for 20 years that is 1,00,000 × (1 + 0.08/12)^240 ≈ ₹4,92,680 — or just use the calculator above.
What is the Rule of 72?+
Divide 72 by your annual rate to estimate doubling time. At 8%, money doubles every ~9 years; at 6%, every 12; at 12%, every 6. It is a mental-math shortcut for the compound interest formula and remarkably accurate between 4% and 15%.
Is daily compounding much better than yearly?+
Slightly, not dramatically. At 8%, daily compounding earns about 0.33% more per year than yearly — roughly ₹330 extra per year on ₹1,00,000. The rate and the time horizon matter far more than the frequency.
What is the difference between simple and compound interest?+
Simple interest is paid only on the original principal; compound interest is paid on principal plus accumulated interest. ₹1,00,000 at 8% for 20 years earns ₹1,60,000 simple but ₹3,92,680 compounded — compounding adds 145% more.
Does this calculator account for inflation or tax?+
It shows nominal growth. To approximate real growth, enter your expected return minus inflation (e.g. 8% − 3% = 5%). For tax, use your after-tax rate — or hold the investment in a tax-sheltered instrument (PPF, ELSS, EPF) where the headline rate is what you keep.
Related calculators
Related articles
Fixed Rate CD Calculator: How to Know What Your Savings Will Actually Pay
Savings & Deposits
PERA Retirement Calculator: How to Map Out Your Personal Equity Retirement Account
Retirement
Pension Drawdown Calculator Aviva: How to Plan Your Retirement Income
Retirement
Calculate My Retirement Date: How to Find Your Real Freedom Number
Retirement