Simple Interest Calculator

What is Simple Interest Calculator?

The Simple Interest Calculator computes interest on the original principal only (no compounding). It is commonly used for short-term loans, some car loans, and informal lending where interest is calculated linearly.

How to Calculate Simple Interest

1. Enter the principal amount
2. Enter the annual interest rate
3. Enter the time period in years
4. Click Calculate to see simple interest and total amount

How Simple Interest Calculator is Calculated

SI = P × R × T / 100, where P = principal amount, R = annual interest rate as a percentage, T = time in years. Total Amount = P + SI.

Worked Example

₹2,00,000 at 10% for 3 years: SI = 2,00,000 × 10 × 3 / 100 = ₹60,000. Total amount = ₹2,60,000. Monthly interest = ₹60,000 / 36 = ₹1,667.

Common Use Cases

• Short-term loan interest estimation
• Flat-rate car loan comparison
• Informal lending calculations
• Teaching basic interest concepts

Common Mistakes to Avoid

• Using simple interest for long-term projections — most financial products use compound interest, so simple interest will underestimate the real cost.
• Confusing a flat-rate car loan (simple interest) with a reducing balance EMI — a 10% flat rate is roughly equivalent to 18–19% reducing balance.
• Forgetting to convert months to years in the formula — if the tenure is 18 months, use T = 1.5 years.
• Assuming all bank products use simple interest — FDs, loans, and savings accounts all use compound interest in India.

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