About this Simple Interest
Simple Interest is calculated only on the initial principal amount. Unlike compound interest, the interest does not earn interest on itself. This is common for short-term personal loans and some auto loans.
How to use this calculator
- Enter the Principal amount (starting balance).
- Enter the Annual Interest Rate.
- Enter the Time period in years.
- The result shows the Total Interest and final Total Amount.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
Inputs explained
Principal
The original sum of money borrowed or invested.
Annual Rate
The percentage rate charged or earned per year.
Time (Years)
The duration of the loan or investment.
Understanding your results
Example scenarios
Personal Loan
Borrow $1,000 at 5% simple interest for 3 years. Interest = $1000 * 0.05 * 3 = $150. Total Payback = $1,150.
Short Term
Invest $500 at 4% for 6 months (0.5 years). Interest = $500 * 0.04 * 0.5 = $10.
Key Features
- Standard I=Prt Formula
- Total Payoff Calculation
- Educational Tool
Things to Keep in Mind
Does not account for compounding periods. For savings accounts or mortgages, use the Compound Interest calculator.
Tips & Best Practices
- Simple interest is always cheaper for borrowers than compound interest over long periods.
- Make sure you know if your loan uses simple or compound interest. Mortgages and credit cards use compound interest.
Glossary of Terms
- Principal
- The initial amount of money.
- Rate
- The percentage of the principal charged as interest each year.
- Term
- The length of time the money is borrowed or invested.