Math Tools
Percentages and unit conversions — the everyday math that's easy to mess up by hand.
The math you look up, not the math you memorize
Percentages and unit conversions are simple in theory and easy to get subtly wrong in practice — mixing up percentage points and percent change, or converting a US recipe measurement into metric without realizing "cup" means different things in different countries. The percentage calculator covers five common modes (X% of a number, percent change, finding the whole, and percentile rank), and the metric converter handles length, weight, volume, and temperature between metric and imperial units, including the Celsius/Fahrenheit/Kelvin conversions that don't follow a simple multiplier.
Percentage & Percentile Calculator
Find X% of a number, percent change, percent off a price, or a value's percentile rank in a data set.
Metric & Imperial Unit Converter
Convert length, weight, volume, speed, and temperature between metric and imperial units instantly — no signup.
Age & Date Difference Calculator
Find your exact age or the time between any two dates in years, months, and days, plus total days, weeks, and months.