Simple Interest Calculator
Interest on the principal only — no compounding.
Enter your values
Enter the principal in $.
Enter the annual rate in %.
Enter the time in years.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Interest
- $750.00
- Final balance
- $5,750.00
- Interest per year
- $250.00
Working
- 1I = $5,000.00 × 0.05 × 3 = $750.00
Quick answer
Simple interest is charged only on the original principal: I = P × r × t.
I = P × r × t
At a glance
| What it does | Interest on the principal only — no compounding. |
|---|---|
| Category | Finance |
| Inputs needed | Principal, Annual rate, Time |
| Main output | Interest |
| Formula | I = P × r × t |
| Cost | Free — no sign-up, no download |
How to use the Simple Interest Calculator
- 1Enter the principal amount.
- 2Add the annual rate and the time in years.
- 3Read the interest and final balance.
Inputs explained
- Principal($)
- Enter the principal in $.
- Annual rate(%)
- Enter the annual rate in %.
- Time(years)
- Enter the time in years.
Worked example
Using the values the calculator loads with:
Inputs
- Principal5000 $
- Annual rate5 %
- Time3 years
Results
- Interest$750.00
- Final balance$5,750.00
- Interest per year$250.00
- I = $5,000.00 × 0.05 × 3 = $750.00
Frequently asked questions
When is simple interest used?
Short-term personal loans, some car loans and most bond coupon payments use simple interest rather than compounding.
How does it differ from compound?
Compound interest earns interest on interest, so over long periods it grows much faster than simple interest on the same rate.
What do I need to enter into the Simple Interest Calculator?
Just 3 values: principal, annual rate, time. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Simple Interest Calculator work out the answer?
Simple interest is charged only on the original principal: I = P × r × t. It applies the formula I = P × r × t and shows the working so you can check each step by hand.
Is the Simple Interest Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.