Loan or Investment Details
Results
Simple Interest Calculator Guide
Calculate simple interest on a loan or investment. Unlike compound interest, simple interest is charged only on the original principal, never on accumulated interest.
Interest = P × r × t, where P is the principal, r the annual rate as a decimal, and t the time in years. The total is P + interest.
How Do I Calculate Simple Interest?
Multiply the principal by the rate and the number of years. For example, $10,000 at 5% for 3 years earns $10,000 × 0.05 × 3 = $1,500 in interest, for a total of $11,500.
Simple vs Compound Interest
Simple interest stays flat because it is always based on the original amount. Compound interest grows faster because it also earns interest on prior interest. Short car loans and some personal loans use simple interest; savings and long-term investments usually compound.
These results are estimates for education and planning, not financial advice. Actual returns, rates, and terms vary — check with a qualified professional before making decisions.
Related: Compound Interest, Loan Payment, and CD Calculator.
Frequently Asked Questions
What is simple interest?
Interest calculated only on the original principal, not on any interest already earned.
What is the simple interest formula?
Interest = principal × rate × time, with the rate as a decimal and time in years.
How is simple interest different from compound interest?
Simple interest is always based on the original amount, while compound interest also earns interest on accumulated interest.
What uses simple interest?
Many car loans, short-term personal loans, and some bonds use simple interest.
Need a Calculator We Don't Have Yet?
Can't find the calculator you need? We'll build it. Submit your request and we'll evaluate it for our growing collection.
Request Calculator