Calculate, Convert and Simplify.
Free calculators, converters and tools to make your everyday life easier.
Explore by category
Each category gathers tools that work well together, with supporting texts so you can study the subject at your own pace.
Math
Percentages, proportions and equations explained step by step.
Explore →Geometry
Areas, volumes and the Pythagorean theorem with figures and examples.
Explore →Physics
Motion and electricity with the basic formulas well explained.
Explore →Conversions
Units of measurement and number bases, from kilometers to binary.
Explore →Daily Life
Dates, deadlines, age and averages for everyday calculations.
Explore →Utilities
Word counter and secure password generator, right in your browser.
Explore →Not sure where to start?
Browse the full catalog and pick a tool by subject. Every one explains the calculation step by step.
Good tools to start with
The most popular with people who are studying or just need a quick calculation.
Percentage Calculator
Part of a value, discount, increase and percent change, with the math shown step by step.
Open tool →Rule of Three Calculator
Simple rule of three, direct or inverse, with the proportion set up and explained.
Open tool →Area and Perimeter Calculator
Rectangle, square, triangle, circle, trapezoid, parallelogram and rhombus, with the formulas on display.
Open tool →Unit Converter
Length, mass, area, volume, speed, time, temperature, data, energy and angle.
Open tool →Date Difference Calculator
Days, months and years between two dates, business days, and how to add or subtract time periods.
Open tool →Secure Password Generator
Strong random passwords, generated in your browser, with a strength estimate in bits.
Open tool →How we work
Three rules we follow on every page.
Every result comes with the step-by-step solution. If the number does not match yours, you can see exactly where the calculations diverged.
The values you type stay on your device. We do not ask for registration and we do not send what you calculate to any server.
Below each tool there are explanations, worked examples, common mistakes and frequently asked questions, with no fluff.