Unit Converter — Length, Weight, Temperature, Volume & Speed

This free unit converter handles the five measurement categories you reach for most — length, weight, temperature, volume, and speed — in one fast, private tool that updates as you type. Enter a value, pick your From and To units, and the answer appears instantly, accurate to six decimal places. Whether you need centimeters to inches for a screen spec, kg to lbs for a shipping label, or Celsius to Fahrenheit for a weather report, this measurement converter gives you the precise figure in one place, without hopping between separate calculators or trusting a rough mental estimate.

The metric and imperial systems stubbornly coexist across the modern world, and that creates daily friction for cooks, travellers, students, engineers, and anyone reading an imported spec sheet. A dependable unit converter removes that friction for good — bookmark this page and every conversion question becomes a two-second lookup.

What Does This Unit Converter Cover?

This all-in-one unit converter spans five categories, each covering the units you meet most in everyday and professional life:

• Length / Distance — metres, kilometres, centimetres, millimetres, miles, yards, feet, inches, and nautical miles.
• Weight / Mass — kilograms, grams, milligrams, metric tonnes, pounds, ounces, and stones.
• Temperature — Celsius, Fahrenheit, and Kelvin.
• Volume — litres, millilitres, cubic metres, US gallons, quarts, pints, cups, and fluid ounces.
• Speed — metres per second, kilometres per hour, miles per hour, feet per second, and knots.

Select any category, enter your value, choose the From and To units, and read the result live. Use the Swap button to flip the conversion direction without re-entering anything — handy when you realise you needed the reverse.

Length Converter — cm to Inches, mm to Inches, km to Miles

The length section handles the most common distance questions. Converting centimeters to inches is one of the highest-volume conversion searches on the planet: one inch equals exactly 2.54 centimetres, so the conversion is precise rather than approximate. The mm to inches conversion is just as common for hardware, manufacturing, and screen dimensions — one inch equals 25.4 millimetres. For travel and navigation, kilometers to miles is essential: one kilometre is about 0.6214 miles, and one mile is about 1.6093 kilometres. Feet, yards, and nautical miles all work the same way — pick your pair and type your number.

Weight Converter — kg to lbs, lbs to kg, Grams to Ounces

The weight converter covers every common mass conversion across metric and imperial. The kg to lbs conversion is among the most searched worldwide — one kilogram equals about 2.2046 pounds — and the reverse, lbs to kg, simply divides by that factor (one pound is 0.4536 kg). For cooking, postal scales, and groceries, grams to ounces is a constant need, at roughly 28.35 grams per ounce. Stones, still used in the UK for body weight, convert at 6.35 kg per stone. Metric tonnes and milligrams round out the set for industrial and scientific work.

Temperature Converter — Celsius, Fahrenheit and Kelvin

Temperature is the trickiest of the five categories because the scales do not share a common zero point, so it needs formulas rather than a single multiplier. Celsius to Fahrenheit uses °F = (°C × 9/5) + 32; Fahrenheit to Celsius uses °C = (°F − 32) × 5/9; and Kelvin adds 273.15 to any Celsius value. Anchor points help: water freezes at 0°C / 32°F and boils at 100°C / 212°F, normal body temperature is 37°C / 98.6°F, and a warm 30°C day is 86°F. This converter runs those formulas exactly, in either direction, the moment you type.

Volume and Speed Converter

The volume converter handles recipes, fuel, and liquid measurements. Litres to gallons is a frequent need for travellers and drivers — one US gallon equals 3.785 litres — while cups, pints, quarts, and fluid ounces complete the US cooking set, all converting instantly to and from metric millilitres and litres. The speed converter spans driving (mph and km/h), aviation (knots), and science (metres and feet per second): one mile per hour equals 1.6093 km/h, and one knot equals 1.852 km/h. From weather reports to speed-limit signs to sailing pace, the pair you need is here.

Metric vs Imperial — Why a Unit Converter Is Essential

According to the National Institute of Standards and Technology (NIST), the International System of Units (SI) — the modern metric system — is the world's most widely adopted measurement standard, used by every country for science, trade, and most official purposes. Yet the imperial system remains deeply embedded in everyday American life, and the UK still mixes both depending on context. That dual reality means conversion questions arise constantly. Unit errors are not just inconvenient, either: the loss of NASA's Mars Climate Orbiter in 1999 was traced to a metric-versus-imperial mismatch between engineering teams. For everyday use, a converter eliminates the risk of a rough guess at the moment precision matters.

How to Use This Measurement Converter

1. Select a category — Length, Weight, Temperature, Volume, or Speed.
2. Enter your value in the number field — the result updates live as you type.
3. Choose your From and To units from the two dropdowns.
4. Read the result instantly — no Calculate button needed.
5. Use Swap to reverse the direction with one click.

Everything runs locally in your browser, so nothing you type is uploaded or stored. For related everyday utilities, try our word counter for writing, the color picker & converter for HEX, RGB and HSL values, the percentage calculator for quick maths, or browse the full free tools hub.

Popular Conversions People Look Up Most

Some conversions come up far more often than others, and it helps to know the exact factors behind them. In length, cm to inches (÷2.54), inches to cm (×2.54), mm to inches, feet to metres, and km to miles dominate everyday searches. In weight, kg to lbs and lbs to kg lead by a wide margin, followed by grams to ounces for cooking and stones to kg in the UK. In temperature, Celsius to Fahrenheit is the classic for weather and cooking, with Fahrenheit to Celsius close behind. In volume, litres to gallons and millilitres to cups top the list for recipes and fuel, while in speed, mph to km/h and knots to mph cover driving and sailing. Every one of these is a single dropdown selection away in the tool above — no formula to memorise.

Common Conversion Mistakes to Avoid

A few pitfalls trip people up repeatedly. The biggest is mixing US and imperial gallons — they are not interchangeable, and the roughly 20% gap can wreck a fuel-economy or recipe calculation. Another is applying a temperature conversion as if it were a simple multiplier: because Celsius, Fahrenheit, and Kelvin have different zero points, you must use the full formula, which this converter does for you. A third is rounding too early — estimating "1 kg is about 2 lbs" is fine for a rough guess but drifts noticeably on larger weights, whereas the precise factor of 2.20462 keeps shipping and freight numbers honest. Using an exact, standards-based converter removes all three risks at once, which matters most when the figure feeds into a purchase, a spec, or a safety margin.

Frequently Asked Questions