Free Unit Converters

Free online unit converters for length, temperature, weight, area, volume, time, and cooking measurements — no sign up, no install, runs instantly in your browser. Whether you're converting metres to feet, Celsius to Fahrenheit, kilograms to pounds, or cups to millilitres, every result is calculated immediately as you type.

These tools cover the conversions people search for most often: the ones that come up mid-recipe, mid-build, mid-workout, or while reading a foreign news article with unfamiliar units. They handle both directions simultaneously, so you never need to re-enter values or flip the tool.

About each converter

Length converter

Converts between metres, centimetres, millimetres, kilometres, inches, feet, yards, and miles — the full set of metric and imperial length units used in everyday and technical contexts.

The most common searches this covers: metres to feet, feet to metres, cm to inches, inches to cm, km to miles, and miles to km. These conversions come up constantly when reading product dimensions listed in the wrong system, understanding heights in a different country's format, or following construction or engineering specs written for a different market.

One thing worth knowing: the US, UK, and metric systems don't map cleanly onto each other, so rounding matters. A door frame specified at 80 inches is exactly 6 feet 8 inches (2,032 mm), but rounded metric conversions like "about 2 metres" miss by 3.2 centimetres — enough to matter in a tight fit. The converter shows full precision so you can round to whatever tolerance your project requires.

Temperature converter

Converts between Celsius, Fahrenheit, and Kelvin. The conversion between Celsius and Fahrenheit is non-linear (multiply by 9/5, then add 32 going one direction; subtract 32, then multiply by 5/9 going the other), which makes it easy to get wrong even if you remember the formula. Kelvin is included for scientific and technical use, where absolute temperature matters.

Common use cases: understanding weather forecasts when travelling, reading oven temperatures in a recipe from another country, and converting body temperature readings between clinical contexts. The crossover point — where Celsius and Fahrenheit read the same number (-40°) — is a useful sanity check if you suspect you've entered the wrong value.

Weight converter

Converts between kilograms, grams, pounds, ounces, and stones. This covers the three weight systems still in active everyday use: the metric system (kg and g), the US customary system (lb and oz), and the British stone system (st), which remains common in the UK for body weight.

Frequent conversions: kg to lbs for gym tracking apps that default to the wrong system, oz to grams for cooking ingredients in imported recipes, and stones to kg for medical or fitness contexts. A person weighing 11 stone is 69.85 kg or 154 lbs — the kind of conversion that's easy to look up but tedious to calculate manually each time.

Area converter

Converts between square metres, square feet, square kilometres, square miles, hectares, and acres.

This comes up most often in property: floor areas are listed in square feet in US real estate listings and square metres almost everywhere else. A 1,500 sq ft apartment is about 139 square metres; a 2,000 sq ft house is about 186. For land, the UK and US use acres while most of the world uses hectares — one hectare is 2.47 acres, one acre is 0.405 hectares. The converter handles all combinations without forcing you to remember which direction each formula runs.

Volume converter

Converts between litres, millilitres, US gallons, imperial gallons, US fluid ounces, UK fluid ounces, cups, pints, and quarts.

Volume is the most fragmented measurement system in everyday use. US gallons and imperial gallons are different (3.785 L vs 4.546 L). US fluid ounces and UK fluid ounces are different (29.57 mL vs 28.41 mL). US cups are 240 mL but some recipes assume 250 mL. The converter distinguishes between US customary and imperial units explicitly, so you get the right result rather than the close-enough one.

The most common use case is recipe conversion: a US recipe calling for 2 cups of stock, 1/4 cup of cream, and 3 tablespoons of butter requires converting all three to metric if you're working with European measuring equipment.

Time converter

Converts between seconds, minutes, hours, days, weeks, and years.

This is more useful than it sounds. In software development, timeouts and cache durations are often written in seconds or milliseconds, but humans think in minutes and hours — the converter bridges the gap instantly. Project planning often involves mixing days and weeks with hours-of-work estimates. Scientific and statistical data may report time spans in seconds that need contextualising into human-readable durations.

One edge case: "years" here uses an average of 365.25 days to account for leap years, which is the right choice for long-duration calculations but worth knowing if you need exact calendar arithmetic.

Cooking converter

Converts between cups, tablespoons, teaspoons, and millilitres for both liquid and dry cooking ingredients.

Liquid ingredients convert straightforwardly by volume. Dry ingredients are more complicated: a cup of flour and a cup of sugar weigh different amounts, and a sifted cup of flour weighs less than a packed one. The converter handles common dry ingredients by weight, using standard density values, which gives a more accurate result than a pure volume conversion.

This tool is most useful when working from recipes that mix measurement systems — a common pattern in adapted or aggregated recipe sites — or when scaling a recipe up or down and needing to convert impractical volumes like "3.5 cups" into something a kitchen scale can handle directly.

Which converter to use

Pick the converter that matches the units you already have. If you know the value in one unit and need the equivalent in another, type it in — the converter updates all outputs simultaneously.

For unit conversions that involve systems you don't use regularly (imperial, stone, US customary gallons), the converter prevents the most common errors: using the wrong gallon definition, forgetting to adjust for the non-linear Celsius/Fahrenheit relationship, or misremembering whether there are 12 or 16 ounces in a pound (the answer depends on whether you mean weight or volume).

A note on precision

All converters display results to several decimal places. For most everyday use — cooking, travel, rough construction estimates — rounding to one or two decimal places is appropriate. For engineering, scientific, or high-tolerance applications, use the full precision shown. The converters do not round internally; what you see is the full calculated result.