Unit Converter, Length, Weight & Temperature

A recipe in grams, an oven in Fahrenheit, a road sign in miles, metric and imperial collide constantly, and guessing the conversion is how cakes fail and luggage gets overweight. This unit converter switches length, weight and temperature between metric and imperial in one step, including an inches to cm calculator with fractions for measurements like 3 1/2", a square feet to cubic yards calculator for projects, plus centimeters to inches, kilograms to pounds, Celsius to Fahrenheit, and back again. Every conversion uses the exact international definitions, 1 inch is precisely 2.54 cm, 1 pound exactly 0.45359237 kg, so there are no rounding surprises, and the result shows the exact rate for 1 unit alongside your answer. Convert between metric (SI) and imperial or US customary units across length, weight, volume, temperature, area and more, every result uses exact, defined conversion factors, not rounded approximations.

Last updated: October 22, 2026

Written by Ateeq Fareedi · Last updated October 22, 2026

The formula

Length: value × from unit in meters ÷ to unit in meters
Weight: value × from unit in kilograms ÷ to unit in kilograms
Temperature: convert to Celsius first, then to the target unit
°F to °C: (°F − 32) × 5/9 · °C to °F: (°C × 9/5) + 32
Kelvin: K = °C + 273.15

A worked example

One mile is exactly 1.609344 km and one kilogram is 2.20462 lb. A room temperature of 68 °F is 20 °C. Converting 5 ft 7 in to metric gives 1.7018 m, about 170 cm, and 10 stone is 63.5 kg.

More about the Unit Converter

Why these conversions are exact, not approximate

Since the 1959 international yard and pound agreement, the inch has been legally defined as exactly 2.54 centimeters, not measured, defined. The pound is exactly 0.45359237 kg. That means inch to cm and pound to kg conversions never drift; the tool computes from full precision definitions and rounds only what it displays.

This is why you can trust the converter for anything from engineering sketches to cooking: the definitions behind it are international law, not somebody's ruler.

Temperature is the odd one out

Length and weight are simple multiplications, but temperature needs formulas: °F to °C is (°F − 32) × 5/9; °C to °F is (°C × 9/5) + 32. So 20 °C is 68 °F, and 68 °F is 20 °C, room temperature in both systems.

Kelvin is simpler still: K = °C + 273.15, no multiplication. And note the trap: a '10 degree rise' in Celsius is an 18 degree rise in Fahrenheit. The converter handles the offset correctly in both directions, which is where mental math usually slips.

Conversions people actually look up

Height: 5 ft 7 in is 1.7018 m, about 170 cm. Weight: 10 stone is 63.5 kg (multiply stones by 14, add pounds). Distance: a mile is exactly 1.609344 km. Cooking: 350 °F is about 177 °C.

A practical tip: convert once and write it down where you will see it, inside the recipe book, on the workshop wall. Looking up the same conversion weekly is a solved problem once you record the answer.

What this converter covers

Three categories: length (mm, cm, m, km, inches, feet, yards, miles), weight (including grams, kg, pounds, ounces, stones) and temperature (Celsius, Fahrenheit, Kelvin).

What it does not cover: area, volume, speed or time. If you need liters to gallons or mph to km/h, that is a different tool. This one stays focused on the three conversions people need daily, and does them exactly.

The rounding trap in chained conversions

Converting inches → cm → inches should return the original number, and it does here because the math runs at full precision before rounding the display. The trap is rounding mid chain: 10 in → 25 cm (rounded) → 9.84 in loses a sixth of an inch to rounding alone.

Rule: never round until the final answer. If you are converting a whole cut list, convert each measurement independently from the original, do not chain conversions through rounded intermediate values.

Cooking conversions that actually work

Oven temperatures: 180 °C ≈ 350 °F (use the converter's exact 356 °F, or just 180/350, ovens are not that precise). Butter: 1 US stick is 113 g; a UK 'half pack' is 125 g, close enough that recipes survive either, but weigh it if the bake matters.

Weights beat volumes for baking: 250 g of flour is always 250 g, while '2 cups' varies by how you scoop. If a recipe gives both, trust the grams. The converter turns the cups into a starting point, not a promise.

Converting for international shipping

Shipping quotes mix units relentlessly: dimensions in cm, weight in kg, but the courier's volumetric formula might want inches and pounds. Convert each measurement before entering it, never trust a quote built on mixed units.

Volumetric weight (length × width × height ÷ a divisor) is where errors cost money: a 2 cm rounding error on each dimension compounds across the formula. Measure carefully, convert precisely, then quote.

Unit conversion in recipes

Baking is chemistry: converting cups to grams (and back) introduces error because a 'cup of flour' varies by how it is packed. For baking, weigh ingredients, 120g of flour is exact; '1 cup' is a guess.

Temperature matters too: 350°F is 175°C, but ovens vary, and the conversion is the least of your worries if your oven runs hot. An oven thermometer beats any conversion chart.

For non baking cooking, approximate conversions are fine, soups and stews forgive. Save the precision for bread, pastry, and anything with yeast or chemical leaveners.

Paper sizes: the A series logic

A series paper (A4, A3..) is brilliantly designed: each size is half the previous, and the aspect ratio (1:√2) stays constant, so scaling A3 to A4 needs no distortion. A4 is 210×297mm; A3 is 297×420mm.

US Letter (8.5×11in) is a different system, slightly wider and shorter than A4. Documents formatted for one look subtly wrong on the other, which is why unit aware templates matter.

When a printer says 'A4' and your file is 'Letter', convert the page size, not just the units, the aspect ratios differ, so it is not a pure unit conversion.

Cups to grams by ingredient (the chart that actually matters)

A cup is a volume, so the grams depend on density: 1 cup all purpose flour is about 120g, granulated sugar about 200g, butter about 227g, honey about 340g, rolled oats about 90g, cocoa powder about 100g.

This is why cup based baking fails across recipes: a cup of flour scooped versus spooned can differ by 30%. For baking, weigh your ingredients; for everything else, the chart gets you close enough.

UK note: British cups in older recipes are often 250ml metric cups while US cups are 236.6ml. A small difference with a real effect in baking, when precision matters, grams win.

Converting both ways

Every conversion has a mirror: km to miles AND miles to km, stone to kg AND kg to stone, grams to ounces AND ounces to grams. The converter handles both directions, just swap the units.

Quick references: 1 km ≈ 0.621 miles; 1 stone = 14 lb ≈ 6.35 kg; 1 oz ≈ 28.35 g; 1 inch = 2.54 cm exactly.

Direction matters: km to miles and miles to km are different searches by different people. A converter that only goes one way answers half the question.

How to use the Unit Converter

Enter the value you want to convert.
Pick the conversion type, length, weight or temperature, and the matching units appear automatically.
Choose the "from" and "to" units, for example meters to feet, kilograms to pounds or Celsius to Fahrenheit.
Press Calculate to see the converted value and the exact conversion rate for 1 unit.

Frequently asked questions

How many cm are in an inch?

Exactly 2.54 cm. That's by international definition since 1959, not by measuring, so every inch to centimetre conversion here is exact, never approximate.

How many pounds are in a kilogram?

2.2046226218 lb, give or take nothing. The converter works from the full precision definition (1 lb = 0.45359237 kg) and only rounds what it shows you.

How do I convert stones to kilograms?

Multiply the stones by 14, add any extra pounds, then multiply that total by 0.45359237. Ten stone works out to 63.5 kg, or pick the imperial weight units above and let the converter do it in one step.

Which units does this converter support?

Length (mm through miles), weight (grams through stones) and temperature (Celsius, Fahrenheit, Kelvin). Area, volume, speed and time aren't covered here, those need a dedicated converter.

How many ounces are in a pound?

There are 16 ounces in a pound, and each ounce is about 28.35 grams. This is the conversion that comes up most when an American recipe meets a kitchen scale, since US butter and flour are often sold and measured in ounces.

How do I convert Fahrenheit to Celsius?

Use (F − 32) × 5/9. So 68°F = (68 − 32) × 5/9 = 20°C. For a quick estimate, subtract 30 and halve it: (68 − 30) ÷ 2 = 19, close enough for weather. To go back: C × 9/5 + 32.

How do I convert miles to kilometers?

Multiply the number of miles by 1.60934 to get kilometers. A 100-mile drive is about 160.9 km. The tool converts instantly in both directions.

How many grams is a cup of flour?

About 120g for all purpose flour, spooned and levelled. Scooping straight from the bag can pack 150g or more into the same cup, weigh it for baking, where the difference matters.

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