Free online calculators, explained step by step
Mortgages, BMI, percentages, unit conversions and more — fast, accurate and free. Every result comes with the formula, the working and an explanation.
Popular calculators
View all →Calculator categories
All categories →Financial Calculators
Plan mortgages, loans, savings, retirement, taxes and investments with free financial calculators.
20 calculators →Health Calculators
Track your body metrics — BMI, calories, ideal weight, heart rate zones and pregnancy milestones.
13 calculators →Math Calculators
Percentages, fractions, averages, exponents, equations and more — with full step-by-step workings.
15 calculators →Conversion Calculators
Convert length, weight, temperature, volume, speed, currency and dozens of other units instantly.
12 calculators →Construction Calculators
Estimate materials for concrete, gravel, paint, tile, roofing and brick projects.
8 calculators →Everyday Life Calculators
Age, dates, time, tips, grades, discounts and bills — quick answers for daily decisions.
10 calculators →Featured calculators
Learn the math behind the numbers
Formulas you can actually follow
Every calculator shows the formula it uses and substitutes your numbers into it, step by step — so you understand the result, not just trust it.
Worked examples in seconds
Each tool walks through a realistic example with the arithmetic written out, turning an abstract formula into something you can reuse.
Expert tips and common mistakes
Short, practical guidance for each calculator — what to watch out for, what the numbers really mean, and where people go wrong.
Why use our calculators?
Instant results
Calculations update live as you type — no waiting, no page reloads.
Trustworthy math
Formulas follow standard industry practice, with the working shown for every answer.
Works everywhere
Perfectly responsive on desktop, tablet and phone — and usable offline after first load.
Recently added
Frequently asked questions
Are the calculators really free?
Yes — every calculator on this site is completely free with no sign-up, no paywall and no download required.
How accurate are the results?
Results follow standard mathematical and financial formulas. Where inputs are estimates (such as tax rates or bag yields), we say so clearly and use realistic defaults.
Do I need to create an account?
No. Nothing is stored, no account is needed, and your numbers never leave your browser.
How do I add a new calculator?
Tell us! We add new calculators regularly based on reader requests — use the contact page to suggest one.