Simple Interest Calculator India — SI Formula & Amount

Last updated: 29 April 2026 Reviewed by Arjun Mehta, CA

**Simple interest (SI)** is calculated only on the original principal, unlike compound interest which also earns interest on accumulated interest. The formula is: SI = (P × R × T) / 100, where P is principal, R is rate per year, and T is time in years. Simple interest is used in short-term personal loans and some government schemes.

Investment Amount (₹) One-time investment

Expected Return (% p.a.)

Tenure (Years)

Maturity Value —

Total Gains —

Annual Return Rate —

View Year-by-Year Breakdown

Real-World Examples — 2026

₹5 lakh investment at 10% for 10 years

₹5 lakh invested at 10% p.a. grows to ₹12.97 lakh in 10 years through compounding. Simple interest would yield only ₹10 lakh — demonstrating the power of compounding over long periods.

₹1 lakh at 12% CAGR over 20 years

₹1 lakh growing at 12% p.a. becomes ₹9.65 lakh in 20 years. Even a 2% difference (at 14%) produces ₹13.74 lakh — demonstrating how small return differences compound dramatically.

Frequently Asked Questions

How accurate is the Simple Interest Calculator?

The Simple Interest Calculator uses standard financial formulas. Results are indicative; actual figures depend on your lender or financial institution's policies.

Is the Simple Interest Calculator free to use?

Yes, the Simple Interest Calculator on CalcPhi is completely free with no registration required.

Are my data inputs stored?

No. All calculations happen in your browser. We do not store any of your financial data.

How often are the Simple Interest Calculator rates updated?

Rates in examples are updated periodically to reflect current market conditions. Always verify with your bank or advisor.

Can I use the Simple Interest Calculator on mobile?

Yes. CalcPhi is fully mobile-optimised. The calculator works on all modern smartphones and tablets.

Who should use this calculator?

Anyone in India planning their finances can benefit from the Simple Interest Calculator. It's designed for both beginners and experienced investors.