🧮 Interest Calculator

Simple Interest Calculator

Calculate simple interest on a loan or investment. Simple interest is calculated only on the original principal — not on accumulated interest.

Simple Interest

I = P × R × T

$
%
0.1%30%
💡 Solve For
Interest Earned
$—
I = P × R × T
Total Amount
$—
Principal
—
Interest
—
Rate
—
Time
—
Principal—
Interest Rate—
Time Period—
Simple Interest (I = PRT)—
Total Amount (A = P + I)—
Annual Interest—

Simple Interest Formula Explained

Simple Interest = Principal × Rate × Time (I = PRT). Unlike compound interest, simple interest does not accumulate — you earn the same amount each period. It's commonly used for car loans, short-term personal loans, and some savings accounts. Use this calculator to find any of the four variables: I, P, R, or T.

FAQ

What is the simple interest formula?
I = P × R × T, where I is Interest, P is Principal, R is the annual rate (as decimal), and T is time in years. Total amount A = P + I.
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest. For the same rate and time, compound interest always grows more.
Where is simple interest used?
Short-term loans, auto loans, some personal loans, and some savings accounts use simple interest. Mortgages and long-term investments typically use compound interest.