Compound Interest Calculator
See how your money grows with this free compound interest calculator. Enter your savings, rate, and monthly contributions to project your balance.
Compound Interest Calculator
Enter your numbers below and hit Calculate — the answer appears instantly, computed entirely in your browser.
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What is Compound interest calculator?
Compound Interest Calculator — See how your money grows with this free compound interest calculator. Enter your savings, rate, and monthly contributions to project your balance.
The math comes from the open-source compound-interest engine (MIT license), which simulates your balance month by month: each monthly contribution is added first, then interest compounds at a monthly rate. Results assume a fixed annual rate, monthly compounding, and contributions made at the start of each month. This is a projection, not a guarantee — real returns vary, and taxes, fees, and inflation are not included.
Why use this compound interest calculator?
Built for compound interest calculator
See how your money grows with this free compound interest calculator. Enter your savings, rate, and monthly contributions to project your balance.
Transparent & honest
Compounds monthly; contributions are added at the start of each month before interest is applied.
Private by design
Everything runs in your browser. Your inputs never leave your device.
Works everywhere
Fully responsive — perfect on desktop, tablet, and mobile. No app needed.
Regularly updated
Regularly maintained and reviewed to ensure accuracy.
Free forever
No accounts, no limits, no watermarks. Use Compound Interest Calculator as much as you need.
How to use Compound Interest Calculator
- 1Enter your "Initial investment ($)" — the lump sum you are starting with.
- 2Type your "Annual interest rate (%)" as a plain number, e.g. 8 for 8%.
- 3Set "Years" to how long the money stays invested.
- 4Optionally add a "Monthly contribution ($, optional)" to model regular deposits.
- 5Run the tool and compare the final balance against your total contributions to see what compounding added.
What can you do with Compound Interest Calculator?
- Compound interest formula — See how your money grows with this free compound interest calculator.
- Investment growth calculator — See how your money grows with this free compound interest calculator.
- How much will savings grow with compound interest — See how your money grows with this free compound interest calculator.
- Monthly compounding work — See how your money grows with this free compound interest calculator.
Good to know
- Compounds monthly; contributions are added at the start of each month before interest is applied.
- Assumes a fixed interest rate for the entire period — real investments fluctuate.
- Ignores taxes, account fees, and inflation, so real purchasing power will be lower.
How it works
The math comes from the open-source compound-interest engine (MIT license), which simulates your balance month by month: each monthly contribution is added first, then interest compounds at a monthly rate. Results assume a fixed annual rate, monthly compounding, and contributions made at the start of each month. This is a projection, not a guarantee — real returns vary, and taxes, fees, and inflation are not included.
Examples
Status: ok — final balance $114,279.24 on $70,000 total contributed ($10,000 initial + $60,000 monthly), earning $44,279.24 in interest.
Status: ok — final balance $16,551.02 with growth from compounding alone; interest earned is $11,551.02.
Status: ok — final balance $9,395.66 on $8,000 total contributed, earning $1,395.66 in interest.
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