The rule of 72
Divide 72 by the yearly rate to estimate how many years it takes money to double: at 6%, about 12 years; at 9%, about 8.
Compound Interest Calculator
See how savings grow with compound interest and regular monthly contributions.
- 100% free
- Monthly contributions
- Yearly growth chart
Balance after 10 years
$54,713.58
- Total contributed
- $34,000.00
- Interest earned
- $20,713.58
- 60.9% on top
Growth by year
- Yr 1$13,201.42
- Yr 2$16,634.27
- Yr 3$20,315.28
- Yr 4$24,262.39
- Yr 5$28,494.83
- Yr 6$33,033.24
- Yr 7$37,899.74
- Yr 8$43,118.03
- Yr 9$48,713.55
- Yr 10$54,713.58
Contributed Interest
Calculation
A = P(1 + r/n)^(nt), plus each monthly contribution compounding from the month it's added
Assumes a constant rate and no taxes, fees or inflation. Real investment returns go up and down.
Last reviewed by the OnlineToolPro team
What is the Compound Interest Calculator?
Shows how money grows when interest earns interest. Add a starting amount, a regular monthly contribution, a yearly rate and how often it compounds, and see the final balance, what you put in and what you earned — year by year.
How it works
How to use the Compound Interest Calculator
3 simple steps. No experience needed.
What can you use it for?
- Plan how much to save each month for a goal.
- See the effect of starting to invest earlier.
- Compare compounding monthly versus yearly.
Good to know
FAQ
Frequently asked questions
What is compound interest?
Interest that's added to your balance, so the next period's interest is calculated on a bigger amount. Over long periods, this snowball effect does most of the growth.
Does compounding more often make a big difference?
A little. At 7% a year, monthly compounding gives an effective yearly rate of about 7.23%. Time and the rate matter far more.
Related guides
Step-by-step help for getting more out of the compound interest calculator.
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Comparison
Simple vs Compound Interest: What's the Difference?
Simple interest is paid on the original amount; compound interest grows on itself. Formulas, a 30-year comparison, APR vs APY, and where each is used.
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