Free calculators · No sign-up · Every formula shown
The exact math behind your money.
Calculators for compounding, FIRE, and investing that show the formula, name every assumption, and walk through the result — so you can check the work instead of trusting a black box.
Worked example — compound interest
$10,000 at 7%, compounded monthly, plus $500/month for 30 years
A = P(1+r/n)nt + PMT·[((1+r/n)nt−1)/(r/n)]
- Total deposits
- $190,000.00
- Interest earned
- $501,150.47
- Future value
- $691,150.47
The formula, on the page. Every tool shows its math and a worked example.
Every assumption named. Rates, timing, and scope limits are labeled, never buried.
Stateless and free. No sign-up, no stored data. Informational, not financial advice.
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