Calculate simple interest and the final amount from a principal, an annual rate and a time in years, with no compounding.
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1,000 at 5% for 3 years earns 150 in interest and totals 1,150. A 20,000 amount at 3.5% for 4 years earns 2,800, for a total of 22,800, while half a year at 5% on 1,000 earns 25.
Simple interest is principal × rate ÷ 100 × years, and the total adds that interest to the original principal. Interest is always calculated on the amount you started with, never on interest already earned, so each full year adds the same amount. Time can be a decimal, so 0.5 represents roughly half a year.
This is an estimate. Fees, taxes, payment timing, day-count conventions and rate changes are not included, and it is not financial advice. A negative rate is accepted and models a steady decline: 1,000 at −2% for 3 years loses 60 and leaves 940.
Enter the principal, the annual rate and the time in years. Simple interest is principal × rate ÷ 100 × years, so 1,000 at 5% for 3 years earns 150 and totals 1,150. The same 150 is added for each full year because interest is always calculated on the original 1,000, never on interest already earned. A 20,000 amount at 3.5% for 4 years earns 2,800, for a total of 22,800.
Time can be a decimal, so half a year at 5% on 1,000 earns 25. Six months is roughly 0.5 years, but lenders may count actual days, so a 182-day period can produce a slightly different figure. Compound interest grows faster: 1,000 at 5% compounded yearly for 3 years reaches 1,157.63, which is 7.63 more than the simple result. Use the Compound Interest Calculator when interest is added to the balance and itself earns interest.
Simple interest appears in some short-term loans, bonds that pay fixed coupons without reinvestment, and informal agreements between people. A negative rate models a steady decline: 1,000 at −2% for 3 years loses 60, leaving 940. The calculator does not include fees, taxes, early repayment or changes in the rate, and it is not a loan offer. Check the agreement to see whether the rate is annual and how days are counted before relying on the figure.
| Input | Result |
|---|---|
1,000 · 5% · 3 y | 1,150 (150) |
1,000 · 5% · 0.5 y | 1,025 (25) |
20,000 · 3.5% · 4 y | 22,800 (2,800) |
1,000 · -2% · 3 y | 940 (-60) |
Simple interest is earned only on the original principal, while compound interest also earns interest on the growth. 1,000 at 5% for 3 years earns 150 here, but compounded yearly it reaches 1,157.63, which is 7.63 more. Use the Compound Interest Calculator when interest is added to the balance.
Yes. Decimal years work, so 0.5 is about six months and earns 25 on 1,000 at 5%. Lenders often count actual days instead, so a 182-day period can differ slightly from the figure here. Check the agreement to see how the period is measured.
It appears in some short-term loans, in bonds that pay a fixed coupon without reinvestment, and in informal agreements between people. Always confirm whether a quoted rate is annual and whether interest is simple or compound before comparing two offers.
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