CALCS

Free · No signup · Step-by-step

Calculators
that explain

Online calculators with formulas, step-by-step solutions, and real-world examples. Finance, math, health, conversions, and engineering.

All categoriesTop calculators

36 calculators across 12 categories · 100% free, no signup

Most popular

The eight most-used calculators on the site

Math
Percentage calculator
Four modes: X% of Y, X is what % of Y, % change, value after adding/subtracting a %
Finance
Mortgage calculator
Monthly payment, total paid, and total interest for a fixed-rate loan
Health
BMI calculator
Body Mass Index from weight and height, with WHO category labels
Finance
Compound interest calculator
Future value of a deposit with optional monthly contributions and configurable compounding frequency
Everyday
Tip calculator
Split a bill across people with a chosen tip percentage
Health
Calorie / BMR calculator
Basal metabolic rate (Mifflin–St Jeor) and daily calorie targets for maintenance and weight loss
Time & Date
Age calculator
Exact age in years, months, days — plus total months, weeks, days, and hours lived
Conversion
Length converter
All-to-all conversion between metric and imperial length units

Calculator categories

Pick a topic — every page has the formula, examples, and FAQ.

Finance

Mortgage, loans, deposits, interest, ROI, taxes

Math

Percentages, fractions, roots, equations, trigonometry

Health

BMI, calories, water intake, ideal weight, BMR

Conversion

Length, weight, temperature, volume, currency

Construction

Tile, paint, concrete, roof, drywall

Engineering

Electricity, resistance, power, torque, heat transfer

Statistics

Mean, variance, p-value, confidence interval

Time & Date

Age, days between dates, time zones, duration

Science

Physics, chemistry, biology, astronomy

Business

Margin, break-even, markup, LTV

Education

GPA, grades, ECTS, study planning

Everyday

Tips, bill split, fuel cost, hourly rate

Why we beat the rest

01

Step-by-step solutions

Not just the answer — every page shows the formula walkthrough so you understand how the number came out.

02

Real examples

Each calculator ships with 2-3 worked examples using realistic numbers, not contrived textbook ones.

03

No junk

No popups, no signup, no server roundtrips for the math — it all runs instantly in your browser.

Common questions

What people usually want to know before they start using the site

  • Yes. Every calculator is free, with no signup, no paywall, no usage limit. There are no ads on the site today, and if we ever add any, they will be a single static slot — no trackers, no behavioral targeting.