Simple Interest Calculator
Simple interest calculator using I = P × r × t. Enter the principal, annual rate and a time in years, months or days to get the interest and the total. How it works
Use the Simple Interest Calculator
About the Simple Interest Calculator
Simple interest is principal × annual rate × time in years: $1,000 at 5% earns $50.00 in 1 year and $250.00 in 5. The simple interest calculator takes the time in years, months or days and returns the interest and the total of principal plus interest.
Simple interest on $1,000
| Annual rate | 1 year | 2 years | 5 years |
|---|---|---|---|
| 3% | $30.00 | $60.00 | $150.00 |
| 4% | $40.00 | $80.00 | $200.00 |
| 5% | $50.00 | $100.00 | $250.00 |
| 6% | $60.00 | $120.00 | $300.00 |
| 7% | $70.00 | $140.00 | $350.00 |
| 8% | $80.00 | $160.00 | $400.00 |
| 9% | $90.00 | $180.00 | $450.00 |
| 10% | $100.00 | $200.00 | $500.00 |
Interest only. Add the $1,000 for the total to repay or receive. Simple interest scales with the principal, so multiply by 10 for $10,000.
Simple interest on $10,000 for 30, 90 and 180 days
| Annual rate | 30 days | 90 days | 180 days |
|---|---|---|---|
| 3% | $24.66 | $73.97 | $147.95 |
| 4% | $32.88 | $98.63 | $197.26 |
| 5% | $41.10 | $123.29 | $246.58 |
| 6% | $49.32 | $147.95 | $295.89 |
| 7% | $57.53 | $172.60 | $345.21 |
| 8% | $65.75 | $197.26 | $394.52 |
| 9% | $73.97 | $221.92 | $443.84 |
| 10% | $82.19 | $246.58 | $493.15 |
Days are divided by 365, with leap days ignored.
Frequently asked questions
- What is the formula for simple interest?
- I = P × r × t, where P is the principal, r the annual rate as a decimal and t the time in years. The total is A = P + I. For $2,500 at 4% for 3 years: 2,500 × 0.04 × 3 = $300.00 of interest and $2,800.00 in total.
- How do I calculate simple interest for months or days?
- Turn the time into years first. Months are divided by 12 and days by 365. $5,000 at 6% for 18 months is 1.5 years and $450.00 of interest. $12,000 at 4% for 45 days is 0.1233 years and $59.18.
- What is the simple interest on $10,000 at 5% for 3 years?
- $1,500.00, for a total of $11,500.00. Every year adds the same $500.00, because interest is charged on the original $10,000 only.
- What is the difference between simple and compound interest?
- Simple interest is charged on the principal only. Compound interest is also charged on the interest already added. $10,000 at 5% for 10 years earns $5,000.00 of simple interest. Compounded once a year the same deposit grows to $16,288.95, which is $1,288.95 more.
- Does it use a 360-day or a 365-day year?
- 365: $10,000 at 6% for 90 days is $147.95. If your contract counts a 360-day year, enter the time as a fraction of a year. 90 ÷ 360 is 0.25 years, which gives $150.00.
- How do I find the rate, the time or the principal?
- This page only works out the interest and the total, so rearrange I = P × r × t by hand: r = I ÷ (P × t), t = I ÷ (P × r) and P = I ÷ (r × t). $360 of interest on $3,000 over 2 years is a rate of 360 ÷ (3,000 × 2) = 0.06, or 6%. Enter 3,000, 6% and 2 years to check: the tool returns $360.00.
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