Unit conversion sounds simple until you are mid-recipe trying to figure out how many cups are in 400ml, or reading a US product spec in a metric country, or checking if your luggage is under the 23kg airline limit when the scale reads in pounds. These are small but surprisingly common daily problems.
A unit converter handles the maths instantly. This guide covers the categories available, the most common conversions people look up, and tips for accuracy.
Most Common Unit Conversions
- Length: km ↔ miles, metres ↔ feet, cm ↔ inches, mm ↔ inches
- Weight: kg ↔ lbs, grams ↔ oz, stones ↔ kg
- Temperature: Celsius ↔ Fahrenheit ↔ Kelvin
- Speed: km/h ↔ mph, m/s ↔ km/h, knots ↔ mph
- Volume: litres ↔ gallons, ml ↔ fl oz, cups ↔ ml
- Data size: GB ↔ MB, TB ↔ GB, bytes ↔ KB
Step-by-Step: Convert Any Unit Free
Go to webtoolsz.com/unit-converter for standard units, or webtoolsz.com/advanced-unit-converter for specialist categories.
Choose from Length, Weight, Temperature, Speed, Volume, Area, Data Size, and more.
Type the number, select the "from" unit and the "to" unit from the dropdowns.
The converted value appears immediately — no button to click, just type and see.
Quick Reference: Common Conversions
- 1 mile = 1.609 km · 1 km = 0.621 miles
- 1 kg = 2.205 lbs · 1 lb = 0.453 kg
- 1 inch = 2.54 cm · 1 foot = 30.48 cm
- 1 US gallon = 3.785 litres · 1 litre = 0.264 US gallons
- 1 GB = 1,024 MB · 1 TB = 1,024 GB
Convert Any Unit — Instantly Free
Length, weight, temperature, speed, volume, data size and more. No sign-up needed.
Open Unit ConverterFrequently Asked Questions
What unit categories does the converter support?
The standard unit converter covers length (metres, feet, inches, miles, km), weight (kg, lbs, grams, oz, stones), temperature (Celsius, Fahrenheit, Kelvin), speed (km/h, mph, m/s, knots), volume (litres, gallons, ml, fl oz), area, and data size. The advanced converter adds 20+ more specialist categories.
Is the unit conversion accurate?
Yes. Conversions use standard internationally accepted ratios — the same values used by NIST and SI definitions. For temperature, the exact formulas are used (not approximations). Results are accurate to the precision needed for everyday and professional use.
Can I convert between US and metric units?
Yes. All conversions between US customary (imperial) and metric (SI) units are supported. Common pairs: km ↔ miles, kg ↔ lbs, cm ↔ inches, litres ↔ gallons, Celsius ↔ Fahrenheit.
Does the tool work offline?
Once the page is loaded, the conversion calculations run entirely in your browser using JavaScript. You do not need an active internet connection to perform conversions after the initial page load.