Simple Interest Calculator
Simple interest calculator
Solve for total, principal, rate, or time with configurable month/day count conventions.
InputsForm5 fieldsLive
Total amount
$5,750.00
Simple interest is not compounded. Formula: I = P × R × T. 3 years = 3 years.
Live update
Interest earned
$750.00
Total amount
$5,750.00
Principal
$5,000.00
Annual rate
5%
Advanced options
- 3 years = 3 years
- Use the same currency or unit for principal, interest, and total amount.
- Convert the annual rate from percent to decimal before applying I = P × r × t manually.
Formula
Interest = P x r x t Total = P + Interest - Convert annual rate to decimal r.
- Multiply principal by rate and normalized years.
- Add interest to principal for total, or solve the missing principal/rate/time from the same identity.
Example
Worked example: 5000 at 5% for 3 years
- 1 I = 5000 x 0.05 x 3 = 750
- 2 Total = 5000 + 750 = 5750
- 3 Interest earned = 750
Interest is 750 and total amount is 5750.
How
- Choose whether to solve for total amount, principal, annual rate, or time.
- Enter the known values and select years, months, or a 360/365-day basis when time is provided.
- Read the solved value, interest earned, and total amount together.
Avoid
- Applying compound formula when simple interest is required.
- Using months as years without conversion.
- Forgetting to convert percentage to decimal in manual calculations.
Ref only. Verify assumptions, fees, taxes.
FAQ
When is simple interest used?
It is used when interest does not compound between periods.
Can I solve for the annual rate or time instead of only the total amount?
Yes. This calculator can solve for principal, annual rate, or time when the other values are known.
Can years be decimal values?
Yes, you can enter partial years such as 1.5.
Is this suitable for all loans?
No, many loans use amortized or compound interest models.
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