Unit Converter

How it works

How to convert units

1. Pick a category — length, weight, temperature, volume, area or speed.
2. Enter a value and choose the unit you're converting from and to.
3. The converted result updates instantly as you type, or use the swap button to reverse direction.

Why it matters

Metric, imperial, and everything in between

Most of the world uses the metric system, while a handful of countries — including the United States — still rely heavily on imperial units for everyday measurements. This tool covers the units people run into most often when cooking, traveling, exercising, or working across both systems.

Because the calculation happens entirely in your browser, your inputs are never uploaded to a server or stored anywhere.

Why temperature works differently

Length, weight, volume, area and speed all convert with a simple multiplication factor, because their scales share a common zero point. Temperature doesn't: Celsius and Fahrenheit start at different points and use different-sized degrees, so converting between them (and Kelvin) uses its own formula rather than a single conversion factor.

Reference

Common conversions

These are the conversions people look up most often. Pick the matching category tab above and the converter will fill in the exact figure — the numbers below are quick reference points.

• Length: kilometers to miles, miles to kilometers, meters to feet, centimeters to inches, inches to centimeters
• Weight: kilograms to pounds, pounds to kilograms, grams to ounces, ounces to grams
• Temperature: Celsius to Fahrenheit, Fahrenheit to Celsius, Celsius to Kelvin
• Volume: liters to gallons, gallons to liters, cups to milliliters
• Area: square meters to square feet, acres to hectares
• Speed: km/h to mph, mph to km/h, knots to mph

Use cases

Where unit conversion matters

Unit conversion comes up more often than most people expect, usually right when you need an answer fast:

• Cooking — converting between cups, milliliters, grams and ounces when following a recipe written for a different measurement system.
• Travel — checking distances in kilometers versus miles, or converting local temperatures to a scale you're used to.
• Fitness — converting run or race distances between kilometers and miles. Pair this with the Step Counter to track distance, or the BMI Calculator for metric or imperial body measurements.
• Shopping and shipping — converting package weights and dimensions between metric and imperial for international orders.
• School and DIY projects — homework, home improvement, and craft projects that mix metric and imperial measurements.

Frequently asked questions

FAQ

Is this unit converter really free, with no sign-up?+

Yes. It runs entirely with JavaScript in your browser, so there is no account, no API key, and no limit on how many times you can use it.

Does my data get sent anywhere?+

No. The conversion happens locally on your device. Nothing is uploaded, stored, or logged.

What categories of units can I convert?+

Length, weight, temperature, volume, area and speed, each with a set of common metric and imperial units to choose from.

How accurate are the conversions?+

Conversions use standard, widely accepted conversion factors and are accurate for everyday use, though results are rounded for readability.

Why is temperature handled differently from the other categories?+

Celsius, Fahrenheit and Kelvin don't share a common zero point, so temperature conversions use their own formulas instead of a simple multiplication factor like the other categories.

Can I use this unit converter offline?+

Once the page has loaded, the conversion logic runs entirely in your browser, so it will keep working even if your connection drops. You do need an internet connection to load the page the first time.

Does the unit converter work on mobile?+

Yes. The layout and category tabs are built to work on phones and tablets as well as desktop, with no app install required.

Related tools

Tools for Numbers and Measurements

• BMI Calculator — work out your Body Mass Index in metric or imperial, using the same unit systems as this converter.
• Step Counter — track steps and distance, then convert the result between kilometers and miles.
• Loan Calculator — work out monthly payments, total interest and amortization.
• Word Counter — live word, character, sentence and paragraph counts.

Methodology

How This Converter Calculates Results

Each category converts through a fixed base unit (meters for length, kilograms for weight, liters for volume, and so on) using standard conversion factors, except temperature, which uses its own formulas because Celsius, Fahrenheit and Kelvin don't share a common zero point. Results are rounded for readability but based on precise, widely accepted conversion factors.

Last updated: August 28, 2026.