Simple Interest Calculator
Results are estimates based on the values you enter. Recheck your inputs and assumptions before using the output for decisions.
Calculate simple interest without compounding.
Simple Interest Calculator
Free online simple interest calculator to estimate simple interest and total amount from principal, annual interest rate, and time in years. This calculator is useful for students, savers, lenders, borrowers, business owners, and anyone who needs a quick way to measure interest without compounding. Simple interest is one of the most basic interest methods in finance because interest is calculated only on the original principal amount. That makes it easy to understand and very practical for short-term loans, basic classroom problems, introductory finance work, and simple agreement reviews.
This calculator uses three main inputs. Principal means the original amount invested, borrowed, or deposited. Annual rate means the yearly interest rate expressed as a percentage. Years means the total time period for which the interest is applied. Once those values are entered, the calculator shows interest and total value. These results help you see both the amount earned or owed as interest and the final balance after adding interest to the principal.
The formula of simple interest
Simple interest = Principal x Annual rate x Time
When the annual rate is entered as a percentage, the formula becomes:
Simple interest = P x R x T / 100
Total amount = Principal + Simple interest
Here P means principal amount, R means rate of interest per year, T means time in years, simple interest means the interest earned only on the original principal, and total amount means the combined value of principal and interest.
Solved Example
Example 1: Find the simple interest if $2,000 is invested for 2 years at 25% per year.
Solve: Simple interest = 2000 x 25 x 2 / 100 = $1,000
Total amount = 2000 + 1000 = $3,000
Example 2: Find the simple interest if $1,000 is invested for 2 years and 6 months at 10% per year.
Solve: Time = 2 + 6/12 = 2.5 years
Simple interest = 1000 x 10 x 2.5 / 100 = $250
Total amount = 1000 + 250 = $1,250
Example 3: Find the simple interest if $5,000 is borrowed for 3 years at 8% per year.
Solve: Simple interest = 5000 x 8 x 3 / 100 = $1,200
Total amount = 5000 + 1200 = $6,200
Table of simple interest calculator
| Principal | Rate | Time (Years) | Simple Interest |
|---|---|---|---|
| $1,000 | 25% | 2 | $500 |
| $1,500 | 25% | 2 | $750 |
| $2,000 | 15% | 3 | $900 |
| $2,500 | 15% | 2 | $750 |
How to use this simple interest calculator
Enter the principal amount in the proper input field. After that, enter the annual interest rate as a percentage value and then enter the time duration in years. Then click the calculate button. The calculator will show the simple interest and the total value in the result box.
This calculator is especially useful when interest is not compounded. In simple interest, the interest amount stays tied to the original principal instead of increasing each period. That makes the math straightforward and easy to verify by hand. It is a good fit for basic interest agreements, classroom work, and quick financial estimates where compounding is not part of the problem.
When using the result, remember that this calculator assumes the interest rate remains constant and that no extra payments or withdrawals happen during the period. If interest is compounded, the final result will be different and usually higher than simple interest for positive rates. Even so, simple interest remains one of the clearest ways to understand how interest works at a basic level, and this calculator gives a quick and practical way to measure both interest earned and final amount.