How do I convert km to miles?

Select Length, enter your km value, set From = Kilometres and To = Miles. 1 km = 0.621371 miles.

How do I convert Celsius to Fahrenheit?

Select Temperature, enter your °C value, set From = Celsius and To = Fahrenheit. The formula is °F = (°C × 9/5) + 32.

How do I convert kg to lbs?

Select Weight, enter your kg value, set From = Kilograms and To = Pounds. 1 kg = 2.20462 lbs.

Math & Numbers

Free Unit Converter

Unit Converter - free online unit converter tool with instant results. Use it for arithmetic, percentage, finance, and numeric problem solving.

No data stored Instant results Mobile-first 100% Free

5 Categories · 40+ Units

Length (8 units)
Weight (6 units)
Temperature (3 units)
Speed (4 units)
Area (6 units)

Unit Converter

Select a category, choose your units, enter a value and click Convert. The result URL is bookmarkable.

What Is a Unit Converter?

A unit converter is a free online tool that instantly converts values between different measurement units across five categories: length (mm, cm, m, km, inches, feet, yards, miles), weight (mg, g, kg, metric tons, ounces, pounds), temperature (Celsius, Fahrenheit, Kelvin), speed (km/h, mph, m/s, knots) and area (cm², m², km², in², ft², acres). Results update live as you type — no button press required.

Unit conversion is needed daily — in cooking, travel, engineering, science and fitness. Our converter covers the most common categories in one clean page, with a swap button to instantly reverse the direction of any conversion.

How to Use the Unit Converter - Step by Step

1

Select a category

Choose from Length, Weight, Temperature, Speed or Area using the category tabs at the top.
2

Enter your value

Type a number in the input field. The result updates instantly as you type.
3

Choose From and To units

Select the source unit and the target unit from the dropdowns. Use the Swap button to reverse them.

Frequently Asked Questions - Unit Converter

: Select Length, enter your km value, set From = Kilometres and To = Miles. 1 km = 0.621371 miles.
: Select Temperature, enter your °C value, set From = Celsius and To = Fahrenheit. The formula is °F = (°C × 9/5) + 32.
: Select Weight, enter your kg value, set From = Kilograms and To = Pounds. 1 kg = 2.20462 lbs.

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Guide & insights

Unit Converter — complete guide

Clear explanations, practical tips and how this free unit converter fits real workflows — optimized for reading on any device.

What is the Unit Converter?

Why people use this calculator

How to use the Unit Converter — summary

Select a category: Choose from Length, Weight, Temperature, Speed or Area using the category tabs at the top.
Enter your value: Type a number in the input field. The result updates instantly as you type.
Choose From and To units: Select the source unit and the target unit from the dropdowns. Use the Swap button to reverse them.

Tips for best results

Double-check classroom or exam problems with a second method when precision matters. Cross-check loan or investment figures with your bank's official schedule — small rounding differences are normal between calculators.