Interest Calculator
Calculate simple or compound interest and find the effective annual rate (EAR).
Enter details and click Calculate
Interest Calculator — FD, RD, and Compound Interest Made Simple
An interest calculator computes the interest earned on an investment or charged on a loan, supporting both simple interest and compound interest calculations. In India, most savings instruments — Fixed Deposits (FDs), Recurring Deposits (RDs), PPF, NSC, and savings accounts — use compound interest with varying compounding frequencies. Understanding how compounding frequency affects your actual returns is essential for comparing financial products accurately.
For a Fixed Deposit of ₹2,00,000 at 7% per annum for 2 years with quarterly compounding: the effective quarterly rate is 7% ÷ 4 = 1.75% per quarter, for 8 quarters. Total amount = ₹2,00,000 × (1.0175)⁸ = ₹2,29,987. Interest earned = ₹29,987. Compare this with annual compounding: ₹2,00,000 × (1.07)² = ₹2,28,980 — ₹1,007 less because quarterly compounding reinvests interest more frequently, earning interest-on-interest within the year. Most Indian bank FDs compound quarterly — this calculator shows you the exact returns.
What is Interest?
Interest is the cost of borrowing money or the reward for lending/saving money, expressed as a percentage of the principal over a specified time period. For borrowers, interest is an expense; for lenders and savers, it is income. Understanding how interest is calculated is fundamental to all financial decisions.
- Simple interest is calculated only on the principal: SI = P × R × T / 100. Compound interest adds the earned interest to the principal for subsequent calculations, creating exponential growth.
- The real interest rate adjusts for inflation: Real Rate ≈ Nominal Rate − Inflation Rate. If your FD earns 7% and inflation is 6%, the real return is only approximately 1%.
- In India, interest earned from savings accounts (up to ₹10,000 under Section 80TTA), bonds, and FDs is taxable. Home loan interest qualifies for deductions under Section 24(b).
- The time value of money principle states that money available today is worth more than the same amount in the future — interest is the mechanism that bridges this difference.
How to Use This Calculator
- Select Simple Interest or Compound Interest using the toggle.
- Enter the Principal Amount (e.g., ₹2,00,000).
- Enter the Annual Interest Rate (e.g., 7%).
- Enter the Time Period in years (e.g., 2 years).
- For compound interest, select the Compounding Frequency (annually, semi-annually, quarterly, monthly).
- Click Calculate to see total interest earned and final amount.
Interest Formulas
- SI = P × R × T ÷ 100 | Total = P + SI
- Compound Interest:
- A = P × (1 + r/n)^(n×t)
- P = Principal | r = Annual rate (decimal) | n = Compounding periods/year | t = Years
- FD Example: ₹2,00,000 at 7% for 2 years, quarterly compounding
- A = 2,00,000 × (1 + 0.07/4)^(4×2)
- A = 2,00,000 × (1.0175)⁸ = ₹2,29,987
- Interest Earned = ₹29,987
Key Terms
- Compounding Frequency
- How often interest is calculated and added to the principal. The more frequently interest compounds, the higher the effective annual rate. A 7% rate compounds to: 7.00% (annual), 7.12% (semi-annual), 7.19% (quarterly), 7.23% (monthly). Indian bank FDs typically compound quarterly.
- Effective Annual Rate (EAR)
- The actual annual return accounting for compounding frequency. Also called XIRR or annualised return in mutual fund terminology. Always compare investments using EAR, not the nominal rate, to make accurate comparisons between products with different compounding frequencies.
- TDS on FD Interest
- Banks deduct TDS (Tax Deducted at Source) at 10% on FD interest exceeding ₹40,000 per year (₹50,000 for senior citizens). To avoid TDS, submit Form 15G (for those with income below the tax threshold) or Form 15H (for senior citizens) to your bank at the start of each financial year.
- FD Interest Tax Treatment
- FD interest is fully taxable as "Income from Other Sources" at your applicable income tax slab rate. Even if TDS is deducted at 10%, if you're in the 30% bracket, you owe an additional 20%. This significantly reduces the effective post-tax return on FD investments, making tax-efficient alternatives like ELSS or PPF more attractive for higher income individuals.
Tips
- Compare FD rates across banks using this calculator — even a 0.25% rate difference on ₹5,00,000 for 3 years amounts to approximately ₹3,800 in additional interest.
- Senior citizens (60+ years) receive an additional 0.25%–0.50% on FD rates from most banks, significantly boosting returns.
- Submit Form 15G/15H at the beginning of each financial year to prevent unnecessary TDS deduction if your total income is below the taxable threshold.
- Consider FD laddering — splitting a large FD into multiple smaller ones with staggered maturity dates to optimise liquidity and take advantage of rate changes.
- For 5-year tax-saver FDs, the principal (up to ₹1.5 lakhs) is deductible under Section 80C, but the interest remains taxable.
- Use the cumulative vs non-cumulative FD option based on your needs: cumulative (reinvested) FDs benefit from quarterly compounding and give higher maturity value; non-cumulative FDs pay interest periodically (monthly/quarterly) as income.
Frequently Asked Questions
Most Indian bank FDs use compound interest with quarterly compounding. The formula is: A = P × (1 + r/4)^(4t), where P is principal, r is annual rate as decimal, and t is time in years. Some post office schemes use simple interest. Always use this calculator to verify the maturity amount shown in the bank's FD receipt, as banks sometimes use slightly different calculation methods for odd-period deposits.
Cumulative FDs reinvest interest each quarter, so you receive the full maturity amount (principal + compound interest) at the end. Non-cumulative FDs pay out interest at regular intervals (monthly, quarterly, or annually) while the principal returns at maturity. Cumulative FDs give higher total returns because of quarterly compounding. Non-cumulative FDs are better for retirees who need regular income. For wealth accumulation, cumulative FDs are more effective.
Banks deduct TDS at 10% when annual FD interest exceeds ₹40,000 (₹50,000 for senior citizens). To avoid TDS: submit Form 15G (for individuals below 60 whose total income is below the tax threshold) or Form 15H (for senior citizens with income below the threshold) to your bank at the start of each financial year. If TDS is already deducted and you are not liable, you can claim a refund when filing your Income Tax Return.
With quarterly compounding, interest is calculated and added to the principal 4 times a year instead of once. Each quarter's interest becomes part of the new principal for the next quarter, so you earn interest on your previously earned interest within the same year. This results in a slightly higher effective annual rate. At 7% nominal rate: annual compounding gives 7% effective return, quarterly compounding gives 7.19% effective return — a small but meaningful difference on large amounts over long periods.
With quarterly compounding at 7.5% for 3 years (12 quarters): A = 5,00,000 × (1 + 0.075/4)^12 = 5,00,000 × (1.01875)^12 = 5,00,000 × 1.25086 = ₹6,25,430. Total interest earned = ₹1,25,430. Note: TDS of 10% would be deducted on interest above ₹40,000 per year unless Form 15G is submitted. After tax at 30% slab, effective post-tax interest = ₹87,801 (30% income tax on ₹1,25,430).