Compound interest calculator
For guidance only. This is not financial advice.
- Total contributed
- Interest earned
View the data in a table
The formula
For a single deposit with no further contributions:
Final balance = P × (1 + r ÷ n)^(n × t)
P is the principal, r the annual rate, n the number of times interest compounds per year and t the number of years. This calculator also adds your monthly contributions at the end of each month.
Worked example
You start with $10,000 and add $200 a month for 20 years at 5% a year, compounded monthly:
- You pay in 10,000 + 200 × 240 = $58,000.
- Your final balance is $109,333.14.
- Interest makes up $51,333.14, or 47% of the total.
Almost half of the result comes from interest, and much of it arrives in the final years. The chart makes that easy to see.
Using the result
Returns are not guaranteed unless a product pays a fixed rate. Try a few scenarios rather than relying on one: change the rate by a point or two, or shorten the time frame.
Read how compound interest works or try the rule of 72. For a specific target, use the savings goal calculator.
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is always calculated on your original deposit. Compound interest is calculated on the deposit plus the interest it has already earned, so your gains accelerate over time.
Does compounding frequency matter?
Yes, but less than you might expect. At the same nominal rate, more frequent compounding gives a higher balance. The rate and the length of time usually matter far more.
Does this include taxes and inflation?
No. Results are before taxes and fees, in future dollars. Use the inflation calculator to see what that money could actually buy.