Simple Interest Calculator
Work out simple interest, where interest is charged only on the original amount, for any number of years, months or days.
- Interest
- –
- Total (amount + interest)
- –
How it is calculated
- Interest = P × r × t
- Total = P + interest
- P = amount, r = yearly rate ÷ 100, t = time in years (months ÷ 12, days ÷ 365)
Worked example
100,000 at 10% a year for 2 years.
| You enter | |
|---|---|
| Amount (principal) | 100,000 |
| Interest rate per year | 10 % |
| Time | 2 |
| Time is in | Years |
| You get | |
| Interest | 20,000 |
| Total (amount + interest) | 120,000 |
100,000 at 10% a year for 2 years earns 20,000 in simple interest, 120,000 in total.
Questions
Simple or compound interest?
Simple interest is charged on the original amount only. Compound interest is also charged on interest already added, so it grows faster. Use the compound interest calculator for savings that compound.
Sources and checks
Last checked: 15 October 2026. This calculator passes 4 automatic tests before every release.
Your numbers never leave your device: the calculation runs in your browser and nothing you type is sent or stored.
Some lenders count a year as 360 days, which gives slightly more interest for a period in days. Results are estimates for information only and are not financial, tax or legal advice. Check important figures with a qualified professional before you act on them.