⭐ Starlight Tools / Simple Interest Calculator

Simple Interest Calculator

Calculate the simple interest and total amount for a loan or investment.

Result:

Understanding Simple Interest

Simple interest is a quick and easy method of calculating the interest charge on a loan. It is determined by the principal amount, the interest rate, and the length of time.

Formulas

The two key formulas for simple interest are:

  • Total Amount: \(A = P(1 + rt)\)
  • Interest Amount: \(I = Prt\)

Where:

  • \(P\) = Principal amount (the initial amount of money)
  • \(r\) = Annual interest rate (as a decimal)
  • \(t\) = Time period (in years)
  • \(A\) = Total amount after interest
  • \(I\) = Total simple interest

How This Tool Works

This calculator operates entirely client-side, ensuring your data remains private and is never sent to a server. It takes the values you enter for Principal, Annual Rate, and Time, and performs the following calculations:

  • The interest rate is automatically converted from a percentage to a decimal (e.g., 5% becomes 0.05).
  • The simple interest is calculated using the formula \(I = Prt\).
  • The total amount is then calculated by adding the interest to the principal, \(A = P(1 + rt)\).