Simple Interest Calculator
Simple interest is calculated only on the original principal amount. Each period earns the same dollar interest regardless of how much has accumulated...
Enter values and click Calculate.
Schedule
Introduction
Simple interest is calculated only on the original principal amount. Each period earns the same dollar interest regardless of how much has accumulated. Short-term personal loans, some bonds, and classroom finance problems often use this method.
What Is Simple Interest?
Simple interest is calculated only on the original principal amount. Each period earns the same dollar interest regardless of how much has accumulated. Short-term personal loans, some bonds, and classroom finance problems often use this method.
Simple Interest Formula
Interest = Principal x Rate x Time. Rate is expressed as an annual percentage; time should match the rate basis (years, months, or days depending on the convention your lender uses).
When Simple Interest Applies
- Some private loans quote flat simple interest.
- T-Bills and discount instruments are often quoted on a simple basis.
- Quick estimates when compounding effects are negligible over a short term.
Simple vs Compound
For multi-year savings goals, compound interest is the realistic model. Simple interest understates growth when earnings stay invested. Use the Compound Interest Calculator for long-term projections.
Practical Example
A $10,000 loan at 8% simple interest for 3 years generates $800 per year ($2,400 total) regardless of payment timing. An amortizing loan at the same APR would allocate interest differently as the balance declines.
Related Tools
Model amortizing loans with the Loan Calculator or Interest Calculator for fixed and periodic contributions.
How It Works
- Enter your amounts, rates, and term in the form. Use the same units shown in the labels (dollars, years, percent).
- Click Calculate to run the Simple Interest Calculator engine. Invalid or empty required fields show a clear error message.
- Review the summary cards for the key outputs. Expand schedules or tables when available for period-by-period detail.
- Copy, print, or share your scenario link. Reset the form anytime to start a fresh comparison.