Simple Interest Calculator
Finance & InvestmentInterest on the principal only — for gold loans, informal lending and quick checks.
Runs entirely in your browser — nothing is uploaded
Features
- The classic P × R × T ÷ 100, worked out instantly.
- Interest per year and per month.
- Shows what the same rate would cost if it compounded.
- Runs entirely in your browser — nothing you enter is uploaded.
How to use the Simple Interest Calculator
- 1Enter the principal, the annual rate and the time in years.
- 2Read the interest and the total repayable.
- 3Check the compound figure beside it if you are not sure which you have been quoted.
Frequently asked questions
What is the simple interest formula?
SI = (P × R × T) / 100, where P is the principal, R the annual rate as a percentage and T the time in years. The total repayable is the principal plus that interest.
When is interest actually simple rather than compound?
Gold loans, many vehicle and personal loans quoted at a "flat" rate, most informal and family lending, and some short-term business credit. Bank deposits, home loans and credit cards all compound. If you are not told which, assume compound and ask.
Why is a flat rate more expensive than it looks?
A flat rate charges interest on the full original amount for the whole term, even though you have repaid much of it. A 10% flat loan over three years costs roughly the same as a 17–18% reducing-balance loan. Always ask for the reducing-balance equivalent before comparing.