Simple Interest Calculator

Simple interest is charged or earned only on the original amount, the principal. Unlike compound interest, the interest itself never earns interest, so the amount grows by the same rupee figure every year.

Results update as you type.

Simple interest

₹13,500

about 13.5 thousand

Principal
₹50,000
Total amount (principal + interest)
₹63,50063.5 thousand
Interest per year
₹4,500

Principal and interest

  • Principal₹50,00078.7%
  • Interest₹13,50021.3%

About this calculator

It is used for some short-term loans and deposits, for interest on late payments in many agreements, and in school maths. Enter the principal, the yearly rate and the time in years, months or days.

How to use it

  1. Enter the principal.
  2. Enter the yearly interest rate.
  3. Enter the time and choose years, months or days.
  4. Read the interest and the total amount.

The formula

SI = P × R × T ÷ 100 Total = P + SI
P
the principal
R
the yearly interest rate in percent
T
the time in years (months ÷ 12, days ÷ 365)

Worked example

₹50,000 at 9% a year

  1. For 3 years: SI = 50,000 × 9 × 3 ÷ 100 = ₹13,500. Total = ₹63,500.
  2. For 90 days: T = 90 ÷ 365 = 0.2466 years. SI = 50,000 × 9 × 0.2466 ÷ 100 = ₹1,110 (₹1,109.59).

What the result means

The interest per year line shows how much the principal earns in every full year. Because nothing compounds, the total interest is just that figure multiplied by the number of years.

If someone quotes a “flat” interest rate on a loan, that is simple interest on the full amount for the whole term. It costs more than the same rate on a reducing-balance loan; use the EMI calculator to compare.

Assumptions

  • The rate stays the same for the whole period.
  • Days are converted to years using 365 days a year.

Limitations

  • Some banks and lenders use a 360-day year or count actual days in a leap year, which changes day-based results slightly.
  • Penalties, fees and taxes are not included.

Frequently asked questions

How do I calculate simple interest for months?

Divide the months by 12 to get years, then use SI = P × R × T ÷ 100. Choosing “Months” here does that for you.

Is simple interest better for a borrower?

At the same rate and on the same declining balance, yes. But many “flat rate” loans charge simple interest on the original amount even as you repay, which works out more expensive.

Where is simple interest used in India?

In some short-term deposits and loans, in interest on overdue bills or tax, and in many school and exam problems. Most bank deposits and home loans use compounding instead.

For information only. This calculator gives estimates based on the figures you enter and the assumptions listed above. It is not financial advice. Actual amounts depend on the lender’s or institution’s terms, fees, rounding and rate changes. Please confirm with them before you decide.

Last reviewed on 1 October 2026. Found a mistake? Tell us.