Enter principal, rate, time and compounding frequency to see your money grow.
How to use the Compound Interest Calculator
- Enter the Principal — the amount you are investing or depositing.
- Enter the Annual Interest Rate and the Time Period in years.
- Choose the Compounding Frequency — annually, half-yearly, quarterly (bank FD style) or monthly.
- Press Calculate Maturity Value — see the final amount, interest earned and the compounding bonus.
The compound interest formula
A = P × (1 + r/n)^(n×t), where P is the principal, r the annual rate, n the compounding frequency and t the years. Each period's interest joins the principal, and the next period earns on the bigger amount — interest earning interest.
Worked example: ₹50,000 at 7% for 5 years compounded annually grows to ₹70,128 — versus ₹67,500 with simple interest. Compounding quietly handed you ₹2,628 extra for doing nothing.
Time is the real multiplier
₹1,00,000 at 8% compounded monthly becomes about ₹2,21,964 in 10 years, ₹4,92,680 in 20 years and ₹10,93,573 in 30 years. The final decade earns more than the first two combined — starting early beats saving more later.
Frequency matters too: monthly compounding beats annual on the same deposit (₹70,128 vs ₹70,881 on the example above), and bank FDs typically compound quarterly, which this calculator models directly.
Frequently asked questions
What is compound interest?
Interest that earns interest. Each period's interest is added to the principal, so the next period's interest is calculated on a larger amount — growth accelerates over time.
How is it different from simple interest?
Simple interest is always calculated on the original principal; compound interest is calculated on principal plus accumulated interest. Over long horizons the gap becomes huge.
How often do bank FDs compound?
Most Indian bank fixed deposits compound quarterly. Choose “Quarterly” in this calculator to match a typical FD.
Which is better — monthly or annual compounding?
Monthly, everything else equal — more frequent compounding means interest starts earning sooner. The difference is small at short tenures but grows with time.
Is this calculator free?
Yes — free, unlimited, private. Nothing is stored or sent.