Unit Conversion Cheat Sheet: Length, Weight, Area, Volume, Speed and Data

The conversions people need most are: 1 inch = 2.54 cm, 1 foot = 30.48 cm, 1 mile = 1.609344 km, 1 kg = 2.20462 lb, 1 US gallon = 3.785 litres, 1 square metre = 10.764 square feet, and °F = °C × 9/5 + 32. The inch, foot, mile and pound (453.59237 g) are exact by definition; the other figures are rounded from exact values given below. Data is the odd one out: "1 GB" can mean 1,000,000,000 bytes or 1,073,741,824 bytes, which is why a new 500 GB drive shows about 465 GB on a computer.

Each section gives the exact factor, a quick mental approximation and a worked example, with a link to the converter that does it. The length converter and its siblings show your value in every unit of that type at once, so one entry answers several questions.

Using the converters

Enter a value, choose the From and To units, and the top line gives the answer; the rows below give the same value in every other unit. Three things to know:

• Results show up to 6 decimal places, without thousands separators.
• Results smaller than 0.000001 show as 0 (0.1 mm shows as 0 km), so convert into a smaller unit when that happens.
• The factors are the exact international definitions, except the ounce, which is stored as 28.349523 g instead of 28.349523125 g. That is why 150 lb shows as 2,400.000011 oz; the answer is 2,400.

Length

Worked example: a height of 5 feet 6 inches is 66 inches, and 66 × 2.54 = 167.64 cm. Entering 5.5 feet in the length converter gives 167.64 cm. The height converter takes feet and inches separately (5 ft 6 in shows 167.6 cm) and works the other way too: 170 cm is 5 feet 7 inches. The height conversion guide lists quick reference heights.

Weight

Worked example: 70 kg in the weight converter is 154.32 lb. In your head, double it and add 10% of the doubled figure: 70 × 2 = 140, plus 14 is 154. Going back, 150 lb is 68.04 kg. The kg to lbs guide has the reverse shortcut and everyday examples.

Volume

Worked example: a 1,000-litre overhead tank holds exactly 1 cubic metre, which the volume converter shows as 264.17 US gallons. For recipes, check whether "cup" means a US cup; weighing in grams avoids the problem entirely.

Temperature

Temperature scales don't share a zero, so you can't use a single multiplier. The formulas are °F = °C × 9/5 + 32, °C = (°F − 32) × 5/9, and K = °C + 273.15. For a rough mental answer, double the Celsius figure and add 30.

Worked example: 100 °F is (100 − 32) × 5/9 = 37.78 °C. The temperature converter shows Celsius, Fahrenheit and Kelvin together, and the Celsius to Fahrenheit guide has more reference points.

Speed

• 1 mph = 1.609344 km/h, so 60 mph = 96.56 km/h and 100 km/h = 62.14 mph.
• 1 m/s = 3.6 km/h exactly. Multiply m/s by 3.6 for km/h, or divide km/h by 3.6 for m/s.
• 1 knot = 1.852 km/h, one nautical mile per hour, used for ships and aircraft.

The speed converter shows all four units together, and the km/h to mph guide lists common speed limits in both units.

Area, including Indian land units

Flats in India are sold in square feet, while plans and records often use square metres, square yards (gaj) or acres. One square metre is 10.7639 square feet; one square foot is exactly 0.09290304 square metres.

Worked examples: a 1,000 sq ft flat is 92.90 square metres in the area converter. A 200 gaj plot is 1,800 sq ft or 167.23 square metres.

The converter covers square metres, square feet, square yards, acres and hectares, but not cents or gunthas. Multiply instead (5 gunthas = 5 × 1,089 = 5,445 sq ft), or convert the acre fraction: 5 gunthas is 0.125 acre, which the converter also shows as 5,445 sq ft. Units such as the bigha, biswa, kanal and marla vary from state to state and sometimes between districts, so there is no single factor. For any legal or purchase purpose, use the area stated in your state's land records or the sale deed.

Data: 1,000 versus 1,024

Storage and speeds use two systems. Drive makers and network speeds use decimal prefixes, where a kilobyte is 1,000 bytes. Many operating systems, including Windows, count in powers of 2, where a "kilobyte" is 1,024 bytes; the strict names for these are kibibyte (KiB), mebibyte (MiB) and so on, but they are usually labelled KB, MB and GB anyway.

The data storage converter uses the binary system (1 GB = 1,024 MB). To see what your computer will report for a new drive, enter the box size in bytes: 500,000,000,000 bytes shows as 465.66 GB, and a 1 TB drive (1,000,000,000,000 bytes) as 931.32 GB. Nothing is missing; the units differ.

Internet speeds are in megabits per second (Mbps), and there are 8 bits in a byte. Divide by 8 to get megabytes per second: a 100 Mbps connection downloads at most about 12.5 MB/s, a little less in practice. For exam photo limits, forms may count 1 KB as 1,000 or 1,024 bytes, so aim slightly inside the limit; the KB image resizer and the photo and signature size guide cover this.

Other handy factors

Frequently asked questions

How many square feet are in a square metre?

10.7639. Multiply square metres by 10.7639 to get square feet, or multiply square feet by 0.0929 to get square metres. A 1,000 sq ft flat is 92.90 square metres.

Why does my 1 TB hard drive show only 931 GB?

The maker counts 1 TB as 1,000,000,000,000 bytes, while your computer divides by 1,024 three times and still calls the result GB. The same bytes come to 931.32 binary gigabytes.

How many cm is 5 feet 6 inches?

167.64 cm. Convert to inches first (5 × 12 + 6 = 66), then multiply by 2.54.

How many square feet is 1 guntha or 1 cent?

A guntha is 1/40 of an acre, or 1,089 sq ft (101.17 square metres). A cent is 1/100 of an acre, or 435.6 sq ft (40.47 square metres).

Is a UK gallon the same as a US gallon?

No. A UK (imperial) gallon is 4.54609 litres and a US gallon is 3.785411784 litres. The converter's gallon is the US gallon.

How do I convert Mbps to MB/s?

Divide by 8, because a byte is 8 bits. 50 Mbps is 6.25 MB/s and 200 Mbps is 25 MB/s, before any overheads.

Sources: NIST Special Publication 811 (exact conversion factors); International Yard and Pound Agreement, 1959; IEC 80000-13 (binary prefixes).