Compound Interest Calculator – Calculate Interest & Growth
Compound Interest Calculator
See how your deposit grows when interest starts earning interest of its own.
Calculate Compound Interest
Choose the compounding frequency your product uses. Results update as you type.
Compound interest is what happens when interest starts earning interest of its own. It's the reason a fixed deposit grows faster than simple arithmetic suggests, and the reason a loan left unpaid for years can balloon far beyond what the rate alone implies. This compound interest calculator shows you the real growth curve, not a flat estimate, for any deposit, investment or compounding loan.
The compound interest formula
P is the principal, r is the annual interest rate (as a decimal), n is how many times per year the interest compounds, and t is the time in years. The interest earned is simply A − P. The part people miss is n: how often compounding happens changes your final number even when the annual rate stays identical.
A worked example: an SBI fixed deposit
Say you invest ₹1,00,000 in an SBI fixed deposit at 6.40% p.a. for 2 years, a rate offered on SBI's 2-to-3-year tenure as of August 2026. SBI, like most Indian banks, compounds FD interest quarterly for any tenure of 6 months or more. This FD compound interest calculator is pre-filled with exactly these numbers.
- Quarterly rate: 6.40% ÷ 4 = 1.60% per quarter.
- Number of quarters: 2 years × 4 = 8.
- Run the formula: A = 1,00,000 × (1.016)^8 ≈ ₹1,13,540.
That's ₹13,540 in interest over 2 years on a ₹1,00,000 deposit, a little more than the ₹12,800 a simple flat calculation of 6.40% × 2 years would give, because each quarter's interest starts earning its own interest from the next quarter onward. Our guide on simple vs compound interest breaks that gap down with more examples.
Why compounding frequency matters
The same 6.40% annual rate produces different maturity values depending on whether it compounds annually, quarterly or monthly, because more frequent compounding means interest starts earning interest sooner. Most Indian bank FDs compound quarterly; some recurring deposits and a handful of specialised products compound monthly. A quarterly compound interest calculator like this one lets you match the compounding frequency to what your actual product uses, rather than assuming annual compounding and underestimating your return. If you want the simple-interest baseline to compare against, the simple interest calculator gives you that side by side.
The same math, working against you
Compounding isn't only good news. On the borrowing side, credit card outstanding balances and some overdraft facilities compound interest, often monthly. That's exactly why unpaid credit card debt grows so much faster than a personal loan at a similar headline rate. The formula is identical; only which side of the transaction you're on changes. For investments, the investment return calculator takes the same compounding math and frames it as annualised return on your portfolio.
Frequently Asked Questions
Is FD interest compounding the same across all banks?
The formula is the same, but the compounding frequency and the rate itself vary by bank and tenure. Always check your specific bank's compounding frequency before comparing FD quotes. A higher rate with less frequent compounding can sometimes underperform a slightly lower rate compounded more often.
Does a cumulative or non-cumulative FD change the compound interest math?
A cumulative FD reinvests the interest each period, so the compound interest calculator above applies directly. A non-cumulative FD pays out interest each period instead of reinvesting it, so you earn simple interest on the principal rather than true compounding. The total payout is lower for the same rate and tenure.
This shows you the interest math. Actual returns depend on your bank's current rates and the specific FD scheme you choose. SBI revises its rates periodically, so reconfirm at the time of investing.