Size and Unit Converter
Convert any measurement between metric and US units, then check the tables for the conversions people look up most: inch fractions in millimeters, screen and paper sizes in centimeters, oven temperatures and kitchen measures.
The key factors are exact by definition: 1 inch = 2.54 cm, 1 foot = 30.48 cm, 1 pound = 0.45359237 kg and 1 US gallon = 3.785411784 liters. To convert °F to °C, subtract 32 and multiply by 5/9. Use the converter below for any value and unit.
- 1 inch
- 2.54 cm (exact)
- 1 foot
- 30.48 cm
- 1 pound
- 0.4536 kg
- 1 US gallon
- 3.785 L
On this page
Unit converter
Pick a measurement type, type a value and choose the two units. The result updates as you type and lists the same value in every other unit of that type.
Length, area, volume, weight and temperature converter
The default shows 12 inches, which is exactly 30.48 cm. Every factor in the converter is the legal definition of the unit, so results are exact up to the seven significant figures shown.
Exact conversion factors
Since the 1959 International Yard and Pound Agreement, the inch, foot, yard and pound have been defined from metric units. These are not approximations, and you can use them to any precision.
| Unit | Metric value | Reverse |
|---|---|---|
| 1 inch | 2.54 cm (25.4 mm) | 1 cm = 0.3937 in |
| 1 foot (12 in) | 30.48 cm (0.3048 m) | 1 m = 3.2808 ft |
| 1 yard (3 ft) | 0.9144 m | 1 m = 1.0936 yd |
| 1 mile (5,280 ft) | 1.609344 km | 1 km = 0.6214 mi |
| 1 square foot | 0.09290304 m² | 1 m² = 10.764 sq ft |
| 1 acre (43,560 sq ft) | 4,046.86 m² | 1 hectare = 2.471 acres |
| 1 cubic foot | 28.317 L | 1 m³ = 35.315 cu ft |
| 1 US gallon (231 cu in) | 3.785411784 L | 1 L = 0.2642 US gal |
| 1 UK (imperial) gallon | 4.54609 L | 1 L = 0.2200 UK gal |
| 1 pound (16 oz) | 0.45359237 kg | 1 kg = 2.2046 lb |
| 1 ounce (weight) | 28.3495 g | 100 g = 3.527 oz |
A room 4 m on each side is 13.12 ft on each side, but its floor is 172.2 sq ft, not 13.12 × 3.28. Convert the lengths first and then multiply, or use 10.764 for area and 35.315 for volume. Getting this wrong is the most common error when ordering flooring, tiles or paint.
Inch fractions in millimeters
Tape measures, drill bits, lumber and hardware in the US use fractions of an inch. These are the exact metric equivalents, plus the nearest standard metric size a European store would stock.
| Inches | Decimal (in) | Millimeters | Nearest metric size |
|---|---|---|---|
| 1/16 | 0.0625 | 1.5875 mm | 1.5 mm |
| 1/8 | 0.125 | 3.175 mm | 3 mm |
| 3/16 | 0.1875 | 4.7625 mm | 5 mm |
| 1/4 | 0.25 | 6.35 mm | 6 mm |
| 5/16 | 0.3125 | 7.9375 mm | 8 mm |
| 3/8 | 0.375 | 9.525 mm | 10 mm |
| 1/2 | 0.5 | 12.7 mm | 12 or 13 mm |
| 5/8 | 0.625 | 15.875 mm | 16 mm |
| 3/4 | 0.75 | 19.05 mm | 19 mm |
| 7/8 | 0.875 | 22.225 mm | 22 mm |
| 1 | 1.0 | 25.4 mm | 25 mm |
"Nearest metric size" is close, not interchangeable. A 6 mm drill bit makes a hole 0.35 mm smaller than a 1/4 in bit, which matters for dowels and anchors. Bit series are compared in the drill bit size guide, and nominal lumber such as a 2 × 4 (actually 1.5 × 3.5 in, 38 × 89 mm) is covered in the lumber size chart.
Common sizes converted to centimeters
Many size names are a single number in inches. Here is what those numbers mean in metric, and which dimension they refer to.
| Size name | What the number measures | Inches | Centimeters |
|---|---|---|---|
| 14-inch laptop | Screen diagonal | 14 in | 35.6 cm |
| 15.6-inch laptop | Screen diagonal | 15.6 in | 39.6 cm |
| 27-inch monitor | Screen diagonal | 27 in | 68.6 cm |
| 55-inch TV | Screen diagonal | 55 in | 139.7 cm |
| 65-inch TV | Screen diagonal | 65 in | 165.1 cm |
| US Letter paper | Sheet width × height | 8.5 × 11 in | 21.6 × 27.9 cm |
| A4 paper | Sheet width × height | 8.27 × 11.69 in | 21 × 29.7 cm |
| Queen mattress | Width × length | 60 × 80 in | 152 × 203 cm |
| 12-inch pizza | Diameter | 12 in | 30.5 cm |
| 22 × 14 × 9 carry-on | Bag height × width × depth | 22 × 14 × 9 in | 56 × 36 × 23 cm |
Screen sizes are diagonals, so the width and height are smaller than the number suggests. The individual guides give the full dimensions: laptop sizes, TV sizes and the A4 paper size.
Height in feet and inches to centimeters
| Feet and inches | Total inches | Centimeters |
|---|---|---|
| 5 ft 0 in | 60 | 152.4 cm |
| 5 ft 3 in | 63 | 160.0 cm |
| 5 ft 4 in | 64 | 162.6 cm |
| 5 ft 6 in | 66 | 167.6 cm |
| 5 ft 8 in | 68 | 172.7 cm |
| 5 ft 10 in | 70 | 177.8 cm |
| 6 ft 0 in | 72 | 182.9 cm |
| 6 ft 2 in | 74 | 188.0 cm |
| 6 ft 6 in | 78 | 198.1 cm |
To convert a height yourself, multiply the feet by 12, add the inches and multiply the total by 2.54. To go back from centimeters, divide by 2.54, then divide by 12: the whole number is feet and the remainder is inches.
Temperature: Fahrenheit, Celsius and kelvin
°C = (°F − 32) × 5/9 and °F = °C × 9/5 + 32. Kelvin is Celsius plus 273.15. The two scales cross at −40, where −40 °F equals −40 °C.
| Reference point | Fahrenheit | Celsius |
|---|---|---|
| Freezer | 0 °F | −17.8 °C |
| Water freezes | 32 °F | 0 °C |
| Refrigerator (food-safe maximum) | 40 °F | 4.4 °C |
| Room temperature | 68 °F | 20 °C |
| Body temperature | 98.6 °F | 37 °C |
| Water boils (sea level) | 212 °F | 100 °C |
| Moderate oven | 350 °F | 177 °C (recipes say 180 °C) |
| Hot oven | 400 °F | 204 °C (recipes say 200 °C) |
| Very hot oven | 450 °F | 232 °C (recipes say 230 °C) |
Fan (convection) ovens run hotter for the same setting, so European recipes often give a fan temperature about 20 °C below the conventional one: 180 °C conventional is roughly 160 °C fan.
Kitchen volume measures
Cup and spoon sizes differ between countries, which explains why some recipes fail when they cross the Atlantic.
| Measure | US | UK, Australia, Canada (metric) |
|---|---|---|
| Teaspoon | 4.93 mL | 5 mL |
| Tablespoon | 14.8 mL (3 tsp) | 15 mL (UK, Canada); 20 mL (Australia) |
| Fluid ounce | 29.57 mL | 28.41 mL (UK) |
| Cup | 236.6 mL (240 mL on nutrition labels) | 250 mL |
| Pint | 473 mL (16 fl oz) | 568 mL (20 fl oz, UK) |
| Gallon | 3.785 L | 4.546 L (UK) |
For baking, weight is more reliable than volume: a US cup of all-purpose flour weighs about 120-130 g depending on how it is filled. Pan sizes and their capacities are in the cake pan size guide.
Size conversions that are not unit conversions
A lot of searches for a "size converter" are about shoes, clothing or rings. Those sizes are counting systems with different starting points, not units, so no single factor converts them. The quick reference below covers adult shoes; each linked guide has the full chart and the body measurement behind every size.
| UK | EU | US men's | US women's | Foot length |
|---|---|---|---|---|
| 4 | 37 | 5 | 6 | 22.9 cm (9.0 in) |
| 6 | 39-39.5 | 7 | 8 | 24.6 cm (9.67 in) |
| 8 | 42 | 9 | 10 | 26.2 cm (10.33 in) |
| 10 | 44.5 | 11 | 12 | 27.9 cm (11.0 in) |
| 12 | 47 | 13 | 14 | 29.6 cm (11.67 in) |
- Shoes: US men's is UK + 1 and US women's is UK + 2. EU sizes step in Paris points of 6.67 mm, UK and US sizes in barleycorns of 8.47 mm (1/3 in). Full chart: shoe size conversion.
- Clothing: a US women's 8 is a UK 12 and an EU 38 or 40 depending on the country. See the clothing size chart and jeans sizes.
- Rings: a US size 7 has a 17.3 mm inside diameter; the ring size chart converts US, UK, EU and Japanese sizes.
The standards behind each of these systems, from ISO 216 paper to Mondopoint shoe sizing, are summarized in the size standards reference.
Frequently asked questions
How do I convert inches to centimeters in my head?
Multiply by 2.5 and add a little: 10 in × 2.5 = 25, and the exact answer is 25.4 cm. For the reverse, divide centimeters by 2.5 and subtract a little: 100 cm ÷ 2.5 = 40, exact answer 39.37 in. The error of the shortcut is about 1.6%.
How many square feet are in a square meter?
1 m² is 10.764 sq ft, and 1 sq ft is 0.0929 m². A 12 × 15 ft room is 180 sq ft, which is 16.7 m². Note that you cannot convert area by converting with the length factor once: you must square it (3.2808² = 10.764).
Is a US gallon the same as a UK gallon?
No. A US gallon is 3.785 L and an imperial (UK) gallon is 4.546 L, about 20% larger. US and UK pints and fluid ounces differ too: a US pint is 473 mL (16 US fl oz), a UK pint 568 mL (20 UK fl oz).
Why is a 65-inch TV not 165 cm wide?
Because the 65 inches (165.1 cm) is the diagonal of the screen. The width of a 16:9 screen is 87.2% of the diagonal, so a 65-inch screen is 56.7 in (144 cm) wide and 31.9 in (81 cm) tall. See the 65-inch TV dimensions.
Can I convert shoe or clothing sizes with a unit converter?
No. Shoe and clothing sizes are label systems, not units, and each country counts differently (a US men's 9 is a UK 8 and an EU 42). Use the shoe size chart or the clothing size chart, which map each label to a body measurement.
How many cm is 5 feet 6 inches?
5 ft 6 in is 66 inches, and 66 × 2.54 = 167.6 cm. Each extra inch adds 2.54 cm, so 5 ft 10 in is 177.8 cm and 6 ft is 182.9 cm.