Unit Converter: Length, Weight, Volume & More (Free)

Whether you are reading a recipe in grams, planning a run in kilometres, or sizing a room in square feet, mixing measurement systems slows you down. This guide shows how to convert any unit quickly and gives you reference tables you can trust. The Unit Converter handles length, weight, volume, area, speed, data and time in one place — free, instant, and entirely in your browser, with no app to install.

How unit conversion works

Every conversion is just multiplication by a fixed factor. Each unit has a known relationship to a base unit in its category — metres for length, grams for weight, litres for volume. To convert, you express the input in the base unit and then into the target unit.

For example, to turn kilometres into miles you multiply by 0.621371, because one kilometre is 0.621371 miles. The maths never changes; only the factor does. A good converter stores accurate factors for hundreds of units so you never have to look them up.

How to use the Unit Converter

It is built to be fast:

1. Open the Unit Converter.
2. Choose a category — length, weight, volume, area, speed, data or time.
3. Enter your value.
4. Pick the unit you are converting from and the unit you want.
5. Read the result instantly, and swap units to convert back.

The answer updates live as you type, so you can compare several units in a row without re-entering anything.

Worked example: 5 kilometres to miles

Suppose your running app shows 5 km and you want miles.

Multiply by the factor 0.621371:

• 5 times 0.621371 = 3.106855

So 5 km is about 3.11 miles. To go the other way, divide by the same factor or multiply by 1.60934: 3.11 miles times 1.60934 is roughly 5 km. The converter handles the rounding so your result is clean and accurate.

Common conversion reference

Handy factors worth keeping nearby:

For anything not listed, the tool covers far more units across every category.

When you will use a unit converter

Conversions come up daily: cooking from an international recipe, shipping a parcel where the carrier wants pounds, comparing fuel economy, sizing furniture for a room, converting file sizes from megabytes to gigabytes, or checking a speed limit abroad. Anyone juggling metric and imperial measurements benefits from one reliable tool rather than searching for a different factor each time.

Tips and common mistakes

Keep these in mind:

• US and imperial gallons differ — a US gallon is about 3.785 litres, an imperial gallon about 4.546. Pick the right one.
• Weight versus mass: pounds and kilograms convert directly here for everyday use.
• For data, remember 1 gigabyte is 1000 megabytes in decimal terms, while some systems use 1024. The tool is explicit about which it uses.
• Watch the unit you select — converting cm to m is easy to mix up with mm.

For temperature specifically, use the dedicated Temperature Converter, and find more free calculators for everything else.

Is it private?

Yes. The Unit Converter calculates everything in your browser with stored conversion factors, so nothing you enter is sent to a server or saved. It keeps working offline once loaded, and your numbers stay yours. Browse the full set of free tools that work the same private, no-sign-up way.