Free · General investment calculators 🤑

Principal & Term Simple Interest Calculator

Calculate interest on a fixed principal without compounding.

  • Formula & worked example
  • Private in your browser
  • No signup
Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Edit a calculated value to solve backwards, or lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

A principal of 1,000 at 5% per year over two years earns or incurs 100 of simple interest. Principal plus interest is 1,100.

Simple interest = principal × rate per period × periods; final balance = principal + interest

Worked example

Enter these known values and leave the other values blank.

Principal
1000 USD
Interest rate
5 %/yr
Term
2:0 yrs / mos
Total interest
100 USD
Final balance
1100 USD
Interest per month
4.17 USD / mos

Assumptions and limitations

  • It is interest on the unchanged principal for one month, not an amortizing repayment that reduces principal. The model excludes fees and compounding. Match rate and term units; years:months accepts values such as 2:0 for two years.
  • Use consistent periods, currency and accounting definitions. The result follows the stated formula and the figures you supply.

Common questions

Is the monthly interest figure a loan repayment?

It is interest on the unchanged principal for one month, not an amortizing repayment that reduces principal. The model excludes fees and compounding. Match rate and term units; years:months accepts values such as 2:0 for two years.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

Explore general investment calculators 🤑 or browse all finance calculators.