How to Convert Units Online Free — Length, Weight, Temperature & More
Unit conversion is one of those tasks that sounds simple until you actually need to do it. Converting kilometres to miles is easy enough. But what about cubic centimetres to fluid ounces? Megapascals to pounds per square inch? Knots to metres per second?
Whether you are cooking with a recipe from another country, filling in engineering specs, understanding a weather report, or shipping a package internationally, unit conversion comes up constantly — and getting it wrong has real consequences.
UtilVox Unit Converter converts between hundreds of unit pairs across all major measurement categories instantly, free, in your browser.
Why Unit Conversion Is Tricky
The world uses two major measurement systems that do not talk to each other neatly:
The metric system (SI) — Used by most of the world. Based on powers of 10, making conversions between metric units straightforward (1 km = 1,000 m = 100,000 cm).
The imperial system — Used primarily in the United States, with partial use in the UK and a few other countries. Based on historical conventions with no consistent relationship between units (12 inches = 1 foot, 3 feet = 1 yard, 1,760 yards = 1 mile).
The lack of a logical relationship between imperial units is why conversion requires lookup tables or a tool — there is no intuitive way to remember that 1 mile = 1.60934 kilometres or that 1 gallon = 3.78541 litres.
Categories Supported by UtilVox Unit Converter
UtilVox Unit Converter covers all major measurement categories:
Length
Convert between millimetres, centimetres, metres, kilometres, inches, feet, yards, miles, nautical miles, and more. Used for everything from measuring a room to calculating a road trip distance.
| From | To | Multiply by |
|---|---|---|
| Miles | Kilometres | 1.60934 |
| Feet | Metres | 0.3048 |
| Inches | Centimetres | 2.54 |
| Yards | Metres | 0.9144 |
Weight and Mass
Convert between milligrams, grams, kilograms, metric tonnes, ounces, pounds, and stones. Essential for cooking, shipping, and fitness tracking.
| From | To | Multiply by |
|---|---|---|
| Pounds | Kilograms | 0.453592 |
| Kilograms | Pounds | 2.20462 |
| Ounces | Grams | 28.3495 |
| Stone | Kilograms | 6.35029 |
Temperature
The only common unit conversion that uses a formula rather than a simple multiplication:
- Celsius to Fahrenheit: °F = (°C × 9/5) + 32
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9
- Celsius to Kelvin: K = °C + 273.15
Quick reference points:
- 0°C = 32°F (water freezes)
- 100°C = 212°F (water boils)
- 37°C = 98.6°F (human body temperature)
- −40°C = −40°F (the point where both scales are equal)
Area
Convert between square millimetres, square centimetres, square metres, hectares, square kilometres, square inches, square feet, acres, and square miles. Used for real estate, agriculture, and flooring.
| From | To | Multiply by |
|---|---|---|
| Acres | Hectares | 0.404686 |
| Square feet | Square metres | 0.092903 |
| Square miles | Square kilometres | 2.58999 |
Volume
Convert between millilitres, litres, cubic centimetres, cubic metres, fluid ounces, cups, pints, quarts, gallons (US and UK), and cubic feet. Critical for cooking, fuel, and liquid measurements.
Note: US and UK gallons are different. 1 US gallon = 3.785 litres. 1 UK (Imperial) gallon = 4.546 litres. The UtilVox Unit Converter handles both.
Speed
Convert between metres per second, kilometres per hour, miles per hour, knots, and feet per second. Used in travel, weather, aviation, and sports.
| From | To | Multiply by |
|---|---|---|
| km/h | mph | 0.621371 |
| mph | km/h | 1.60934 |
| Knots | km/h | 1.852 |
| m/s | km/h | 3.6 |
Digital Storage
Convert between bits, bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, and their binary equivalents (kibibytes, mebibytes, etc.). Essential for understanding file sizes, storage capacity, and data transfer rates.
How to Convert Units with UtilVox
UtilVox Unit Converter is designed to be as fast as possible to use.
Step 1 — Open the converter
Go to utilvox.com/tools/unit-converter. No login required.
Step 2 — Select the measurement category
Choose from length, weight, temperature, area, volume, speed, digital storage, pressure, energy, or power.
Step 3 — Enter your value
Type the number you want to convert into the input field. The converter shows the result in all available units for that category simultaneously — so you see all conversions at once rather than having to select each one individually.
Step 4 — Copy your result
Click any result to copy it to your clipboard. Use it in your document, spreadsheet, or wherever you need it.
Real-World Use Cases
Cooking with international recipes
A French recipe calls for 250g of flour. Your measuring cups only have ounce markings. 250 grams = 8.82 ounces.
A US recipe calls for 2 cups of milk. Your measuring jug is in millilitres. 2 US cups = 473 ml.
International shipping
You are shipping a package that weighs 4.5 lbs to a country that uses kilograms for customs declarations. 4.5 lbs = 2.04 kg.
Weather and travel
The weather forecast in a country you're visiting says 28°C. In Fahrenheit that is 82.4°F — a warm day, but not hot enough to worry about.
Your rental car shows speed in km/h. The speed limit is 60 mph. 60 mph = 96.56 km/h — you need to stay below 96 on the display.
Fitness and health
Your workout app tracks distance in kilometres but you are used to miles. 5 km = 3.11 miles.
Your body weight is 75 kg. A US fitness website asks for your weight in pounds. 75 kg = 165.35 lbs.
Real estate and construction
A property listing gives the floor area in square feet. You need square metres to compare with other listings. 1,200 sq ft = 111.48 m².
Common Conversion Mistakes to Avoid
Confusing mass and weight — In everyday use, people say "weight" when they mean "mass." 1 kg of feathers and 1 kg of steel have the same mass. The distinction matters in physics but not in most practical conversions.
US vs UK gallons and fluid ounces — A US fluid ounce is 29.57 ml; a UK fluid ounce is 28.41 ml. A US gallon is 3.785 litres; a UK gallon is 4.546 litres. Always check which standard a recipe or spec uses.
Celsius vs Kelvin in scientific contexts — Temperature differences work the same in Celsius and Kelvin (a change of 1°C = a change of 1 K), but absolute values are different. Water freezes at 0°C = 273.15 K.
Binary vs decimal storage units — 1 kilobyte can mean either 1,000 bytes (SI standard) or 1,024 bytes (binary standard, properly called a kibibyte). Hard drive manufacturers use decimal (so a "1 TB" drive holds 1,000 GB in decimal), while operating systems often display in binary (so the same drive shows as ~931 GB).
Related Tools
If you need more specialised conversions, UtilVox has dedicated tools:
- Currency Converter — Live exchange rates for 160+ currencies
- BMI Calculator — Calculates BMI from height and weight in either metric or imperial
- Calorie Calculator — Uses metric or imperial inputs for personalised calorie targets
Summary
Unit conversion should take seconds, not minutes of searching and calculating. Whether you need metric to imperial, temperature, area, volume, or digital storage, UtilVox Unit Converter shows all conversions at once the moment you type your value.
Convert any unit free with UtilVox — no login, no ads, works instantly in any browser.
