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From everyday percentages to loan repayments and health metrics — accurate calculators with clear, explained results.
Popular Calculators tools
Percentage Calculator
Work out percentages, increases, decreases and changes.
BMI Calculator
Calculate Body Mass Index in metric or imperial units.
Unit Converter
Convert length, weight, temperature and data units.
Age Calculator
Find your exact age in years, months, days and more.
Tip Calculator
Work out tips and split the bill in seconds.
Percentage Increase Calculator
Calculate percentage increase or decrease between two numbers.
Date Difference Calculator
Count the time between two dates precisely.
Discount Calculator
See sale prices, stacked discounts and savings.
Business Days Calculator
Count working days between dates, or add business days to a date.
Random Number Generator
Generate cryptographically secure random numbers with unique and sorted options.
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Percentage Increase Calculator
Calculate percentage increase or decrease between two numbers.
Business Days Calculator
Count working days between dates, or add business days to a date.
Random Number Generator
Generate cryptographically secure random numbers with unique and sorted options.
Age Calculator
Find your exact age in years, months, days and more.
Learn about Calculators
How to Calculate Percentages: 3 Formulas with Examples
The three percentage formulas, worked examples, common mistakes, and the difference between percent and percentage points.
What Is BMI? Formula, Categories and Limitations
How body mass index is calculated, what the categories mean, a worked example, and the limits of BMI as a health measure.
How Age Is Calculated in Years, Months and Days
How an exact age is worked out from two dates, why months make it tricky, and how to count down to a birthday.
Counting Days Between Dates: Inclusive vs Exclusive
Should you count the first day, the last day or both? How inclusive and exclusive day counting differ, plus leap years and business days.
How to Calculate a Tip and Split the Bill
The simple maths behind a tip, a worked example for splitting a bill, and a rough guide to tipping customs around the world.
How to Calculate a Discount, Stacked Deals and Sales Tax
How percentage discounts are worked out, why two stacked discounts are less than their sum, and where tax fits in.
Unit Conversion Basics: Length, Weight, Temperature and Data
The conversions worth knowing by heart, why temperature needs a formula and not a single factor, and a quick worked example.
How Random Number Generators Work (and What Makes a Draw Fair)
The difference between Math.random and cryptographic randomness, how to draw numbers without repeats, and why random and fair are not the same thing.
How Many Days Between Two Dates? (Calculator + Manual Method)
Calculate exact days between two dates: understand inclusive vs exclusive counting, leap years, working days, and manual calculation formulas.
Calculators FAQ
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