Free online calculators that show their work
170 free calculators across finance, math, health, conversions, construction, science and everyday life. Every calculator shows its formula and a worked example, so you can trust — and check — the answer.
Most used calculators
Mortgage Calculator
Monthly payment, total interest and full cost of a home loan.
BMI Calculator
Body mass index from your weight and height, with the standard weight category.
Compound Interest Calculator
How money grows when interest earns interest, with optional regular contributions.
Percentage Calculator
Find X% of a number, or work out what percent one number is of another.
Age Calculator
Exact age in years, months and days from a birth date.
Length Converter
Convert mm, cm, metres, kilometres, inches, feet, yards, miles and nautical miles.
Concrete Calculator
Cubic yards, cubic feet and bags of concrete for a slab, footing or post hole pad.
Salary to Hourly Wage Calculator
Convert an annual salary to hourly, weekly and monthly pay.
Categories
Finance
Loans, interest, savings, taxes, investing and everyday money math — with amortization-grade accuracy and the formulas shown.
Math
Percentages, fractions, statistics, geometry and algebra tools with step-ready formulas and worked examples.
Health & Fitness
BMI, calories, body composition, pregnancy dates and training metrics based on published formulas.
Date & Time
Age, date differences, business days, time zones and calendar questions answered precisely.
Unit Conversions
Length, weight, temperature, volume and 20+ other unit conversions using exact international factors.
Construction & Home
Concrete, paint, tile, roofing and material estimators for DIY and professional projects.
Science
Physics and chemistry calculators — electricity, motion, energy, gases and solutions.
Everyday Life
Grades, pets, bills, trips and household math — small questions, exact answers.
Calculators by country
United States
US Dollar (USD) · Imperial / US customary units
United Kingdom
Pound Sterling (GBP) · Metric with common imperial usage
Canada
Canadian Dollar (CAD) · Metric (official) with imperial in daily use
Australia
Australian Dollar (AUD) · Metric
India
Indian Rupee (INR) · Metric
All country hubs
Local units, currencies and conventions, explained.
Why CalcHub?
Plenty of sites will give you a number. We think you deserve the workings too: every calculator on CalcHub prints the exact formula it uses and a worked example with real numbers, and our formula library is covered by automated tests with known answers. If a result matters — a loan, a tax estimate, a building project — you can verify it yourself before you rely on it.