Compound Interest Calculator
Compound Interest Calculator is a free online tool to calculate your investment returns over time
Growth over time
Year by year
| Year | Deposits | Interest | Low | Expected | High |
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How this is calculated
Your annual rate is converted into the growth that happens each month for the compounding frequency you pick, using (1 + r/n)^(n/12) − 1. Each month the balance grows, then your contribution is added (or added first, if you choose start of month). Fees reduce growth each month. Contributions rise once a year by the percentage you set. With a withdrawal, the balance stops at zero instead of going negative. Inflation, when switched on, divides each future amount by (1 + inflation)^years.
Doubling time is shown two ways: the Rule of 72 shortcut (72 ÷ rate) and the exact figure from your effective yield.
About compound interest
What is compound interest?
Compound interest is interest earned on both your original money and on the interest it has already earned. Each period your balance grows a little more than the last, so the longer you stay invested, the faster it climbs.
The compound interest formula
For a single deposit, the final amount is calculated with the formula below. P is the starting amount, r is the annual rate as a decimal, n is how many times interest compounds each year and t is the number of years.
A = P × (1 + r/n)^(n×t)Example: $10,000 at 7% compounded annually for 10 years grows to $19,671.51.
The Rule of 72
A quick way to estimate how long money takes to double is to divide 72 by the annual interest rate. At 8% a year, money doubles in about 9 years. The calculator above shows both this estimate and the exact doubling time.
Does compounding frequency matter?
Compounding more often earns slightly more, but the gap between monthly and daily compounding is small. The interest rate, the length of time and the size of your regular contributions make a much bigger difference.
Fees and inflation
Annual fees reduce the growth your money earns each year, and inflation reduces what your final balance can buy. Use the fee field and the "today's money" option to see results after both.
Low, expected and high scenarios
Real returns are never fixed. The rate variance setting shows what your savings could look like if the rate comes in below or above your estimate, so you can plan for a range instead of a single number.
This website is designed to help you quickly and easily calculate investment returns with regular deposits or withdrawals, fees and inflation, across a low, expected and high rate. Estimates only. Returns are not guaranteed and real investments rise and fall. This is general information, not financial advice.