343 calculators · every answer shows its formula
Don't just get the answer.
See the work.
A tested program runs every calculation — and the formula, the steps, and the source sit right on the page. So you can trust the number, not just take it.
- tested formulas
- 7,173
- automated tests
- categories
- 10
- in-depth guides
- 168
- no account · private
- $0
Live — BMI Calculator, no sign-up
Most used
Browse by category
- Finance 84 Personal finance, investments, loans, and real estate finance calculators.
- Health & Fitness 34 BMI, calorie, body fat, pregnancy, and wellness calculators.
- Everyday 36 Age, percentage, tip, word count, and everyday utility tools.
- E-Commerce 13 Profit margin, Amazon FBA, ROAS, break-even, and business calculators.
- Mathematics 88 Algebra, geometry, statistics, and number theory tools.
- Home DIY 14 Paint, tile, concrete, lumber, and renovation estimation tools.
- Automotive 13 Auto loan, MPG, depreciation, lease vs. buy, and vehicle calculators.
- Engineering 25 Ohm's law, voltage drop, wire sizing, MTBF, and fluid mechanics tools.
- Industrial & Trades 22 Pressure, torque, energy, electrical, and industrial unit converters.
- Developer Tools 14 JSON formatter, regex tester, UUID generator, and other developer utilities.
Numbers you can actually trust
Every result here is a tested program — not a language-model guess. That's the difference between a calculator and asking an AI to "do the math."
- Tested, not guessed 7,173 automated tests. Deterministic math — never a hallucinated number.
- Shows the work Every formula, worked example, and source is on the page — not a black box.
- Sourced & checkable Where a formula has an authoritative source, it’s cited on the page — so you can verify it yourself.
- Private by default Runs in your browser. Your inputs never leave your device. No account.
Latest guides
All 168 →-
Finance · 8 min
How to Use an Amortization Calculator to Save Thousands on Your Mortgage
An amortization calculator reveals something your lender won't: exactly how much interest you can sa…
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Finance · 7 min
APR vs Interest Rate: What Is the Difference and Why It Matters
APR and interest rate are often used interchangeably, but they mean very different things. Understan…
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Health & Fitness · 7 min
What Your BMI Really Means (And Its Limitations)
BMI is the most widely used health screening metric in the world. It is also one of the most misunde…
Questions, answered
- Are the calculators free?
- Yes — all 343 of them, with no account, no sign-up, and no paywall.
- Can I trust the results?
- Every formula is a tested program, not a language-model guess — backed by 7,173 automated tests, with the formula and its source shown on each page. The math is deterministic: the same inputs always give the same answer. See how we build and verify calculators on our methodology page.
- Is my data private?
- Completely. Every calculation runs inside your browser — your numbers are never sent to a server, and nothing is stored about you.
- Do they work on mobile?
- Yes. Every calculator is fully responsive and loads fast, because pages are static and ship almost no JavaScript.