Numbers
Compound Interest Calculator
Used by developers, writers, and creators worldwide.
A compound interest calculator shows how a starting balance plus regular monthly contributions grows over time once interest is added on top of interest. Enter your starting amount, monthly contribution, an annual interest rate, and a number of years, and it compounds the balance month by month to project the final total. It also breaks out how much you actually paid in versus how much the interest added, so you can see the power of compounding clearly. Savers use it to plan a nest egg, students to understand why starting early matters, and anyone comparing accounts to gauge long-term returns. Compounding rewards time more than any other factor, which is why small monthly amounts left untouched can grow into surprisingly large sums. Use it to set a realistic target, test different rates, or simply see how your savings might develop year after year.
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How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Enter your starting amount and monthly contribution.
- Set the annual interest rate and number of years.
- Click Generate to project the growth.
- Compare contributions against interest earned.
Use Cases
- •Projecting how a savings account grows over years
- •Seeing the long-term impact of monthly contributions
- •Understanding why starting to save early matters
- •Comparing accounts with different interest rates
- •Setting a realistic long-term savings target
Tips
- →Even small monthly amounts compound into large sums over decades.
- →Try a higher rate to see how returns change the outcome.
- →Longer time horizons matter more than larger contributions.
- →Remember the result is before tax and inflation.
FAQ
how is the interest compounded
The calculator compounds monthly: each month it adds one twelfth of the annual rate to the running balance, then adds your contribution. Monthly compounding is a common, realistic assumption for savings accounts and reflects how most banks credit interest.
does it account for taxes or inflation
No. The projection shows nominal growth before any tax on interest and before inflation reduces purchasing power. Treat the result as a gross estimate and adjust for your own tax situation and expected inflation.
is this financial advice
No. This tool is for illustration and education only. It produces estimates based on the numbers you enter, not a guarantee of returns, and is not financial advice. Consult a qualified professional before making investment decisions.
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