Compound Interest Calculator
Compound interest means you earn interest on your interest. Enter your starting balance, how much you add each month, the annual return and the number of years to see your future balance and how much of it comes from growth.
Result
How compound interest is calculated
With no regular deposits, the formula is FV = P × (1 + r/n)^(n×t), where P is the starting balance, r the annual rate, n the number of compounding periods per year and t the years. This calculator also adds your contribution at the end of each month and compounds monthly or annually, whichever you choose.
A quick example
Starting with $1,000, adding $100 a month and earning 7% compounded monthly, you would have about $19,318 after 10 years. You would have put in $13,000, so more than $6,000 is growth. The longer the time frame, the larger the share that comes from interest.
What to keep in mind
The rate you enter is an assumption. A savings account or CD pays a known APY, while investments in a 401(k) or IRA go up and down from year to year and can lose value. The result is not adjusted for inflation, taxes or fees.
Related guide: How Compound Interest Works
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is always calculated on the original principal. Compound interest is added to the balance and earns interest itself, so growth speeds up over time.
Does compounding frequency matter?
A little. At the same nominal rate, monthly compounding ends slightly higher than annual compounding because interest starts earning interest sooner.
What is the Rule of 72?
It is a shortcut for estimating how long it takes money to double: divide 72 by the annual return. At 6%, it takes roughly 12 years.
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Results are estimates for informational purposes only and are not financial, tax, legal or medical advice.