Interest Calculator

Use this interest calculator to estimate how a starting balance grows with simple or compound interest. Enter a principal amount, annual interest rate, time period, and interest type to compare final amount, total interest, effective rate, and the original principal.

How to use this calculator

Choose Simple Interest or Compound Interest, then enter the principal, annual rate, and number of years. For compound interest, select daily, weekly, monthly, quarterly, semi-annually, or annually. The calculator returns the final amount, total interest earned, effective rate, principal, and time period.

Formula

Simple interest:

$final\ amount = principal \times (1 + rate \times years)$

Compound interest:

$final\ amount = principal \times (1 + rate \div n)^{n \times years}$

Here, n is the number of compounding periods per year. For example, 10,000 dollars at 5 percent for 5 years becomes 12,500 dollars with simple interest, or about 12,833.59 dollars with monthly compounding.

Comparing scenarios

Compounding frequency matters most when the rate or time period is higher. For goal planning, compare this page with the compound interest calculator and savings goal calculator. If the interest relates to borrowing instead of saving, the loan calculator may be a better fit.

Important context

This calculator assumes fixed inputs. It does not include taxes, account fees, inflation, promotional rates, variable APR changes, or investment risk.