# Compound Interest Calculator

> Calculate compound interest with recurring contributions. Free compound interest calculator with the formula shown - runs entirely in your browser, no signup.

- **Canonical URL:** https://boringtoolskit.com/compound-interest/
- **Category:** Finance & Investing
- **Evidence level:** authored-methodology
- **Reviewed:** July 26, 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

FV = principal x (1 + r/12)^(12n) + contribution x (((1 + r/12)^(12n) - 1) / (r/12)) for monthly contributions.

## Worked example

$10,000 principal with $200 monthly contributions at 7% for 20 years: $58,000 contributed grows to about $144,572.72, of which $86,572.72 is interest.

## Assumptions

- The interest rate and contribution remain constant.
- Taxes, fees, inflation, and market volatility are excluded.
- The projection is illustrative and is not a forecast or guaranteed return.

## Common questions

### Why can compounding frequency change the result?

More frequent compounding changes the effective annual yield when the nominal rate is held constant.

### What does contribution timing change?

A beginning-of-month contribution earns one additional month of modeled growth compared with an end-of-month contribution.

### Is the chart an investment forecast?

No. It visualizes constant-rate arithmetic and does not model market variability or losses.

## Related tools

- /apy-calculator/
- /future-value-calculator/
- /savings-goal-calculator/

## Sources

- [Compound Interest Calculator](https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator)
- [Understanding interest](https://www.consumerfinance.gov/consumer-tools/)

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*Local planning estimate. Verify current terms, rates, and policies before acting.*