Simple interest calculator
Enter the principal, the yearly rate and the time. The page shows the simple interest and the amount, then the amount at the same rate compounded yearly, quarterly, monthly and daily.
- Any rate and period
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How to use it
- Enter the principal and the yearly rate.
- Enter the time in years, months or days.
- Read the simple interest, the amount, and the compound amounts at the same rate.
Simple interest, and compound interest at the same rate
Simple interest is principal × yearly rate × time in years. Months count as twelfths of a year, so 18 months is 1.5 years. Days use a 365-day year, so 365 days is one year. A principal of 10,000 at 5% for 3 years earns 1,500 of simple interest, and the amount is 11,500.
The compound rows keep that principal, rate and time, and compound the rate yearly, quarterly, monthly or daily. At 5% for 3 years the yearly compound amount is 11,576.25, the quarterly amount is 11,607.55, the monthly amount is 11,614.72 and the daily amount is 11,618.22. The compound-interest page adds monthly deposits and a goal.
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Questions
Which row is the simple-interest answer?
Simple interest and the amount with simple interest are the simple-interest result. The later rows are the compound amounts at the same rate.
How are months and days turned into years?
Months are divided by 12. Days are divided by 365.
What does monthly compounding mean?
The yearly rate is split into twelve, and that monthly rate is applied at the end of each month.
Can the rate be zero?
Yes. The interest is zero and every amount equals the principal.