Finance
Compound Interest Calculator
Project investment growth with regular compounding and contributions.
Use the tool
Enter your values below. Inputs stay in your browser.
Instant result
Projected balance
$63,367.82
Assumes a constant entered return and end-of-month contributions; excludes taxes and fees.
Total contributions
$40,000.00
Estimated growth
$23,367.82
A projection, not a guaranteed investment return.
If the return is 6% instead
$59,163.80
Same deposits, one point lower — the sensitivity of your plan.
If the return is 8% instead
$67,932.91
Same deposits, one point higher.
Starting amount doubles in
9.9 years
At the entered return, ignoring contributions.
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Transparent methodology
What the result includes—and what it does not
Built for savers and investors projecting how a starting amount plus monthly contributions grows, and how sensitive the outcome is to the assumed return.
Calculation method
- 1The selected nominal compounding convention (daily to yearly) is converted to an equivalent monthly rate so the opening balance and end-of-month contributions grow on one curve.
- 2The projected balance combines compound growth of the principal with the future value of the contribution stream; growth is the balance minus everything you deposited.
- 3The +/-1 point scenarios recompute the identical deposit plan one percentage point below and above the entered return, and the doubling time uses the effective annual rate.
Assumptions and limits
- A constant return every period - real investments vary year to year and can lose money.
- Taxes, fees, and inflation are excluded; contributions are treated as end-of-month deposits.
- A planning projection, not investment advice or a guaranteed outcome.
Worked example
Monthly contribution projection
Input: $10,000 starting amount, $250 monthly, 7% annual return compounded monthly for 10 years.
Output: About $63,368 projected: $40,000 contributed plus about $23,368 growth; the same plan lands near $59,164 at 6% and $67,933 at 8%.
How to use it
Three steps. One clear answer.
- 1Enter or paste the values requested by the tool.
- 2Review the input units and choose any relevant options.
- 3Calculate, then copy or download the result you need.
Built for trust
Useful without the friction.
- No registration or paywall before your result.
- Responsive controls for phone, tablet, and desktop.
- Clear assumptions and warnings where estimates have limits.
Frequently asked questions
How does the Compound Interest Calculator work?
The selected nominal compounding convention (daily to yearly) is converted to an equivalent monthly rate so the opening balance and end-of-month contributions grow on one curve. The projected balance combines compound growth of the principal with the future value of the contribution stream; growth is the balance minus everything you deposited. The +/-1 point scenarios recompute the identical deposit plan one percentage point below and above the entered return, and the doubling time uses the effective annual rate.
What should I check before using the result?
A constant return every period - real investments vary year to year and can lose money. Taxes, fees, and inflation are excluded; contributions are treated as end-of-month deposits. A planning projection, not investment advice or a guaranteed outcome.
How current is this page?
The methodology and source notes were reviewed on 2026-07-25. Editable rates and inputs should still be checked against the provider or authority linked below.
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