Simple Interest Calculator

Calculate simple interest and total returns with dedicated Month Mode (% per month) and Year Mode (% per annum). Store customer records, view exact timestamps, and export history.

Calculation Details

Calculation Mode
Save calculation under customer or friend's name for organized history.
₹
%
Mode A: Interest rate per month (e.g. 2% or 5% per month).
Enter duration in total months.

Calculation Result

Ready to Calculate

Fill in the principal, interest rate, and duration on the left, then click Calculate Interest to see your detailed breakdown.

Calculation History 0

No calculations saved yet. Calculate simple interest above to view history.

Month Mode vs. Year Mode Explained

In Indian informal finance, rural lending, and community borrowing (such as vyaj or village lending), interest is traditionally calculated on a monthly rate basis:

  • Month Mode: The entered interest rate is directly applied per month (e.g. 2% or 5% per month). If ₹10,000 is borrowed at 5% per month for 12 months, the simple interest is exactly ₹6,000 (total ₹16,000).
  • Year Mode: The entered interest rate represents the annual percentage rate (APR) commonly used in formal banking, fixed deposits, and government schemes. If ₹10,000 is borrowed at 5% per year for 1 year, the simple interest is ₹500 (total ₹10,500).

Utility Seva provides distinct toggles so you never have to manually divide or multiply rates.

Formulas & Calculation Rules

Both modes follow standard mathematical definitions:

  • Simple Interest (SI):
    SI = (P × R × T) / 100
  • Total Repayment Amount (A):
    A = Principal + Simple Interest
  • P (Principal): The initial sum of money borrowed or invested.
  • R (Rate of Interest): Expressed as a percentage per period (per month in Month Mode; per year in Year Mode).
  • T (Time Period): Number of time periods (months in Month Mode; years in Year Mode).

What is the difference between Simple Interest and Compound Interest?

With Simple Interest, interest is earned or paid strictly on the original principal amount for the entire duration. In Compound Interest, accumulated interest from previous periods is added back into the principal, resulting in interest on interest.

Is my financial data or customer names uploaded to any server?

No. Utility Seva operates on 100% client-side privacy. All calculations and history entries are stored solely in your browser's local storage (localStorage) on your computer. Nothing is ever transmitted to an external server.

Can I enter decimal amounts and fractional durations?

Yes. You can enter fractional numbers for principal (e.g. ₹15,450.50), interest rates (e.g. 2.75%), and durations (e.g. 1.5 years or 6.5 months).