Unit Converter

What Is Unit Conversion?

Unit conversion is the process of expressing a measured quantity in a different unit without changing the quantity itself — turning 5 kilometers into 3.1069 miles, or 100°C into 212°F. Most conversions work by relating each unit to a common base: for length the base is the meter, for weight the kilogram, for volume the liter, and so on. To convert from one unit to another you scale the value into the base unit using the source unit's factor, then scale out of the base using the target unit's factor. Temperature is the exception, since its scales have different zero points and so use formulas rather than a single multiplier.

Because measurement systems grew up independently around the world, the same physical thing is described by metric units in most countries and by imperial or US customary units elsewhere. Reliable conversion bridges that gap, whether you are reading a foreign recipe, following an engineering spec, comparing product dimensions, or interpreting a weather report. This converter handles seven everyday categories — length, weight, temperature, area, volume, speed, and time — with the standard internationally agreed factors built in.

How to Use This Unit Converter

Pick a category from the bar at the top — Length, Weight, Temp, Area, Volume, Speed, or Time. Type the amount into the left value box and choose its unit from the left dropdown, then select the unit you want in the right dropdown; the converted result appears instantly in the read-only right box. The conversion runs as you type, so there is no button to press.

Use the ⇄ swap button to flip the two units and reverse the conversion. Below the inputs, a formula line restates the result in plain language, and the All conversions grid shows your value expressed in every unit of the selected category at once, with the source unit highlighted, so you can compare them at a glance.

Real-World Use Cases

• Cooking and baking — convert between cups, tablespoons, milliliters, and liters to follow recipes from any country.
• Travel and navigation — switch between kilometers and miles, or km/h and mph, when reading foreign road signs and speedometers.
• Home and DIY projects — convert inches to centimeters or square feet to square meters when measuring rooms and materials.
• Weather and science — translate Celsius, Fahrenheit, and Kelvin when reading forecasts or lab data.
• Shipping and logistics — convert grams, pounds, kilograms, and metric tons to check weights and limits.

Tips for Accurate Conversions

• Confirm the category first — entering a length value while Weight is selected will convert it as a weight.
• Use the swap button instead of retyping when you realize the units are the wrong way round.
• Note that volume units like cup, pint, quart, and gallon here use US measures, which differ from UK imperial equivalents.
• Treat the month and year time units as fixed 30-day and 365-day approximations, not calendar-exact values.
• Use the "All conversions" grid to sanity-check a result against neighboring units before relying on a single number.

Features

• Seven categories — length, weight, temperature, area, volume, speed, and time.
• Instant, as-you-type conversion — results update the moment you change the value or units.
• Swap button — reverse the source and target units in one click.
• Plain-language formula — a readable restatement of the conversion below the inputs.
• All-conversions grid — your value shown in every unit of the category at once, with the source highlighted.
• Accurate temperature handling — Celsius, Fahrenheit, and Kelvin converted with proper non-linear formulas.
• 100% client-side — your data never leaves your browser.

Frequently Asked Questions

How accurate are the conversions?

The converter uses standard, internationally agreed conversion factors and computes with JavaScript's floating-point math, which is accurate to roughly 15 significant digits — far more precision than everyday use requires.

Why does the tool show every unit at once?

The "All conversions" grid below the converter displays your input value in every unit of the selected category and highlights the source unit, so you can compare related units side by side without doing one conversion at a time.

Are the volume units US or UK measures?

The cup, pint, quart, and gallon units use US customary measures. UK imperial versions of these units are slightly larger, so keep that in mind when working with British recipes or specifications.

How are temperatures converted?

Temperature does not use a simple multiplier because its scales have different zero points. The tool converts your value to Celsius as a base using the correct formula, then to the target scale, so Celsius, Fahrenheit, and Kelvin all convert correctly.

How long are a "month" and a "year" in the time category?

They are fixed approximations: a month is treated as 30 days and a year as 365 days. They are convenient for rough estimates but do not account for varying month lengths or leap years.

Does this converter work offline and keep my data private?

Yes. All calculations run in JavaScript inside your browser, so nothing you enter is sent to a server. Once the page has loaded, the converter continues to work even without an internet connection.