Calculators Tools
4 free calculators tools, all running privately in your browser.
These free calculators cover everyday math beyond a basic keypad: percentages, tips, BMI, age, and more. Each shows its working so you can follow the logic, and all of them run instantly in your browser with no signup.
Some calculations - reverse percentages, tip splitting, BMI - are easy to get subtly wrong by hand. These tools apply the correct formula every time. Our guide on percentage math covers the reverse-percentage trap that catches almost everyone.
Age Calculator
Calculate exact age from a birth date.
BMI Calculator
Calculate Body Mass Index (metric or imperial).
Percentage Calculator
Calculate percentages, increases, and decreases.
Prime Number Checker
Check if a number is prime and find its factors.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in meters squared. In imperial units it's (pounds × 703) ÷ (inches²). The BMI calculator handles both and shows your category.