See how your money grows over time. This free compound interest calculator lets you add a starting deposit and regular monthly contributions, choose how often interest compounds, and instantly see your future value and total interest earned.
Your investment
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Future value
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Enter a deposit, rate and years
Initial deposit
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Total contributions
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Total invested
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Interest earned
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Results update automatically as you type. Estimates only — actual returns vary and are not guaranteed.
Use this free compound interest calculator to see how your money grows over time. Enter a starting deposit, an optional monthly contribution, your interest rate and the number of years to find your future value — plus exactly how much of it is interest.
What this compound interest calculator shows you
A compound interest calculator estimates the future value of your savings or investment when interest is earned on both your principal and your accumulated interest. Enter your initial deposit, regular contributions, interest rate, time period and compounding frequency, and it returns your future value, total invested and total interest earned.
Compound interest is often called the eighth wonder of the world because it accelerates over time. The longer your money stays invested, the larger the share of your balance that comes from interest rather than your own contributions.
How to use the compound interest calculator
Enter your initial deposit. The amount you’re starting with today.
Add a monthly contribution (optional). Any amount you’ll add regularly.
Set the interest rate and time period. Your expected annual rate and how many years you’ll invest.
Choose how often interest compounds — daily, monthly, quarterly or yearly.
Read your result. Your future value and total interest update instantly.
How compound interest is calculated
The compound interest formula for a single deposit is:
A = P × (1 + r ÷ n)n × t
Where:
A = the final amount (future value)
P = the principal (your starting deposit)
r = the annual interest rate (as a decimal)
n = how many times interest compounds per year
t = the number of years
When you add regular contributions, each deposit also earns compound interest from the moment it’s added — which is why this calculator includes a monthly contribution field.
Compound interest example
Suppose you invest $10,000, add $100 a month, and earn 7% per year compounded monthly for 10 years:
Detail
Amount
Initial deposit
$10,000
Total contributions
$12,000
Total invested
$22,000
Interest earned
$15,405
Future value
$37,405
You put in $22,000, but compounding adds another $15,405 on top — and that gap grows dramatically the longer you stay invested.
Why compounding frequency matters
The more often interest compounds, the faster your money grows, because interest starts earning its own interest sooner. The effect of daily versus yearly compounding is small at low rates but adds up over long periods.
Compounding
$10,000 at 7% for 10 years
Yearly
$19,672
Quarterly
$20,016
Monthly
$20,097
Daily
$20,137
The power of starting early
Time beats timing. An extra 10 years invested often matters more than a higher rate.
Contribute consistently. Regular monthly deposits compound alongside your principal.
Reinvest your returns. Compounding only works if interest stays invested.
Mind the rate. Even 1–2% more per year becomes a large gap over decades.
Compound interest terms glossary
Term
What it means
Principal
The original amount you deposit or invest.
Compound interest
Interest earned on both your principal and your past interest.
Future value
What your investment will be worth at the end of the period.
Compounding frequency
How often interest is added — daily, monthly, quarterly or yearly.
APY
Annual percentage yield — the real yearly return after compounding.
Rule of 72
Divide 72 by your rate to estimate the years it takes to double your money.
Compound Interest Calculator FAQ
How is compound interest calculated?
Compound interest uses the formula A = P × (1 + r ÷ n)n × t, where P is your principal, r is the annual rate as a decimal, n is how many times interest compounds per year, and t is the number of years. Interest is earned on both your principal and your previously earned interest.
What is the difference between simple and compound interest?
Simple interest is earned only on your original principal. Compound interest is earned on your principal plus all previously accumulated interest, so your balance grows faster over time.
How does compounding frequency affect my returns?
The more often interest compounds, the faster your money grows, because interest starts earning its own interest sooner. For $10,000 at 7% over 10 years, yearly compounding gives about $19,672 while daily compounding gives about $20,137.
Does this calculator include monthly contributions?
Yes. You can add a regular monthly contribution, and each deposit earns compound interest from the moment it's added, alongside your initial principal.
What is the Rule of 72?
The Rule of 72 is a quick way to estimate how long an investment takes to double. Divide 72 by your annual interest rate — at 8%, your money roughly doubles every 9 years.
Is compound interest calculated before or after tax?
This calculator shows growth before tax and fees. Your real return may be lower once taxes, investment fees and inflation are taken into account.
Is the compound interest calculator free to use?
Yes, this compound interest calculator is completely free, needs no sign-up, and gives instant results directly in your browser.
