What are these calculators?
These are free, browser-based calculation tools designed for everyday tasks — no installation, no account, no data sent to a server. Each calculator runs entirely in JavaScript in your browser. They cover the most common calculation needs: math (percentage, discount), personal health (BMI, age), finance (loans, tips), unit conversion, date arithmetic, and number systems. Results update as you type, so you get answers instantly.
Financial and money calculators
The Percentage Calculator handles the three most common percent operations in one tool. The Tip Calculator makes splitting restaurant bills effortless with preset and custom tip percentages. The Discount Calculator shows exactly how much you save at any sale percentage — and can reverse-calculate the original price if you only see the tagged sale price. The Loan Calculator uses standard amortization to show monthly payments and total interest for any loan size, rate, and term.
Date and time tools
The Age Calculator gives your exact age in years, months, and days along with a next-birthday countdown. The Days Between Dates calculator finds the precise difference between any two calendar dates in days, weeks, and months — useful for project timelines, billing periods, and deadlines. The Time Zone Converter supports 26 major world timezones and handles daylight saving time automatically, making international scheduling straightforward.
Unit conversion and number tools
The Unit Converter covers the four most-needed measurement categories: length (mm to miles), weight (mg to tonnes), temperature (°C, °F, Kelvin), and speed (m/s to knots). The BMI Calculator computes Body Mass Index from height and weight and shows the WHO weight category with color coding. The Roman Numeral Converter translates between standard decimal numbers and Roman numerals in both directions, with full validation to ensure correct notation.