How to use the Simple Interest Calculator
- Enter principal and annual interest rate.
- Enter time and pick the unit.
- Read the interest and total amount.
How it works
SI = P × R × T ÷ 100, where P is principal, R the annual rate in percent and T the time in years. Total amount A = P + SI. Months are divided by 12 and days by 365.
Worked example
Principal 50,000 at 7.5% for 3 years: SI = 50,000 × 7.5 × 3 ÷ 100 = 11,250, so the total repayable is 61,250.
Good to know
Simple interest grows in a straight line, unlike compound interest which grows exponentially.
Use it to check loan quotes, bond coupons and short-term deposits.
Enter time in years, months or days; the tool converts for you.
Frequently asked questions
SI = P × R × T ÷ 100.
Simple interest uses only the principal; compound interest also earns interest on past interest, so it grows faster.
Divide the months by 12 to get years, then apply the formula.
Results are estimates for information only and are not financial, tax or legal advice.