Unit Conversion Cheat Sheet: Common Conversions With Formulas
To convert between units, multiply by the conversion factor for that pair. The most useful ones are exact: inches × 2.54 gives centimeters, pounds × 0.45359237 gives kilograms, and miles × 1.609344 gives kilometers. Temperature is the exception because the scales start at different zero points, so use °C = (°F - 32) × 5/9 instead of a single multiplier.
This page collects the most common conversions for length, weight, volume, temperature, speed, area and digital storage, with worked examples you can check by hand. The inch, foot, yard, mile and pound factors are exact by international definition (the 1959 agreement fixed the yard at 0.9144 m and the pound at 0.45359237 kg), and the other factors follow the NIST conversion tables, rounded for readability. For instant results with any value, use our Unit Converter.
Length Conversions
Metric units
| From | To | Multiply by |
|---|---|---|
| Kilometers | Meters | 1,000 |
| Meters | Centimeters | 100 |
| Centimeters | Millimeters | 10 |
| Meters | Millimeters | 1,000 |
Metric and imperial
| From | To | Multiply by | Example |
|---|---|---|---|
| Inches | Centimeters | 2.54 (exact) | 12 in = 30.48 cm |
| Feet | Meters | 0.3048 (exact) | 6 ft = 1.83 m |
| Yards | Meters | 0.9144 (exact) | 100 yd = 91.44 m |
| Miles | Kilometers | 1.609344 (exact) | 5 mi = 8.05 km |
| Kilometers | Miles | 0.621371 | 10 km = 6.21 mi |
| Centimeters | Inches | 0.393701 | 180 cm = 70.87 in |
Mental math: 1 inch is about 2.5 cm, 1 foot is about 30 cm, and 1 mile is about 1.6 km. For a rough kilometers-to-miles conversion, multiply by 0.6.
Weight (Mass) Conversions
| From | To | Multiply by | Example |
|---|---|---|---|
| Ounces (oz) | Grams (g) | 28.3495 | 8 oz = 226.8 g |
| Pounds (lb) | Kilograms (kg) | 0.45359237 (exact) | 150 lb = 68.04 kg |
| Kilograms (kg) | Pounds (lb) | 2.204623 | 70 kg = 154.32 lb |
| Grams (g) | Ounces (oz) | 0.035274 | 500 g = 17.64 oz |
| Stones | Kilograms (kg) | 6.35029 (1 stone = 14 lb) | 10 st = 63.5 kg |
| Metric tons (tonnes) | Pounds (lb) | 2,204.62 | 1 t = 2,204.62 lb |
| US short tons | Kilograms (kg) | 907.185 (1 short ton = 2,000 lb) | 1 short ton = 907.18 kg |
Mental math: 1 kg is about 2.2 lb. To convert kilograms to pounds, double the number and add 10%. To convert pounds to kilograms, halve it and subtract 10%: 150 lb becomes 75 - 7.5 = 67.5 kg, close to the exact 68.04 kg.
Volume Conversions
These are US customary units.
| From | To | Multiply by |
|---|---|---|
| Teaspoons (tsp) | Milliliters (mL) | 4.92892 |
| Tablespoons (tbsp) | Milliliters (mL) | 14.7868 |
| Fluid ounces (fl oz) | Milliliters (mL) | 29.5735 |
| Cups | Milliliters (mL) | 236.588 |
| Pints (liquid) | Liters (L) | 0.473176 |
| Quarts (liquid) | Liters (L) | 0.946353 |
| Gallons | Liters (L) | 3.78541 |
| Liters (L) | Gallons | 0.264172 |
Cooking shortcut: 1 cup is about 240 mL, 1 tablespoon about 15 mL, 1 teaspoon about 5 mL and 1 gallon about 3.8 L. UK (imperial) units are larger: an imperial gallon is 4.54609 L and an imperial pint is 568 mL, compared with 473 mL for a US pint. Our Volume Converter and Cooking Converter handle both systems.
Temperature Conversions
Temperature needs a formula because the Fahrenheit, Celsius and Kelvin scales have different zero points:
Fahrenheit to Celsius: °C = (°F - 32) × 5/9
Celsius to Fahrenheit: °F = (°C × 9/5) + 32
Celsius to Kelvin: K = °C + 273.15
Fahrenheit to Kelvin: K = (°F - 32) × 5/9 + 273.15
Quick reference
| Description | °F | °C | K |
|---|---|---|---|
| Absolute zero | -459.67 | -273.15 | 0 |
| Water freezes | 32 | 0 | 273.15 |
| Room temperature | 68 to 72 | 20 to 22 | 293 to 295 |
| Average body temperature (traditional value) | 98.6 | 37 | 310.15 |
| Water boils (sea level) | 212 | 100 | 373.15 |
Oven temperatures
| °F | °C (rounded) |
|---|---|
| 325 | 163 |
| 350 | 177 |
| 375 | 191 |
| 400 | 204 |
| 425 | 218 |
| 450 | 232 |
Mental math for °F to °C: subtract 30, then halve. For 70°F that gives (70 - 30) ÷ 2 = 20°C, against an exact 21.1°C. It works best near room temperature and drifts further off at extremes. The Temperature Converter gives exact values for any temperature.
Speed Conversions
| From | To | Multiply by | Example |
|---|---|---|---|
| mph | km/h | 1.609344 (exact) | 60 mph = 96.56 km/h |
| km/h | mph | 0.621371 | 100 km/h = 62.14 mph |
| km/h | m/s | 0.277778 | 36 km/h = 10 m/s |
| m/s | km/h | 3.6 (exact) | 10 m/s = 36 km/h |
| Knots | km/h | 1.852 (exact) | 30 knots = 55.56 km/h |
| Knots | mph | 1.150779 | 30 knots = 34.52 mph |
Handy references: 100 km/h is about 62 mph and 60 mph is about 97 km/h. The speed of sound in dry air at 20°C is about 343 m/s, which is roughly 1,235 km/h or 767 mph.
Area Conversions
| From | To | Multiply by |
|---|---|---|
| Square feet (ft²) | Square meters (m²) | 0.092903 |
| Square meters (m²) | Square feet (ft²) | 10.7639 |
| Acres | Hectares | 0.404686 |
| Hectares | Acres | 2.47105 |
| Square miles | Square kilometers | 2.58999 |
| Square kilometers | Square miles | 0.386102 |
| Square inches | Square centimeters | 6.4516 (exact) |
Real estate context: 1 acre is 43,560 ft² and 1 hectare is 10,000 m², or about 2.47 acres. A soccer pitch of 105 m by 68 m covers 7,140 m², about 1.76 acres.
Digital Storage Conversions
Storage uses two systems. The decimal (SI) system multiplies by 1,000 at each step. The binary system (IEC prefixes, with an "i" in the name) multiplies by 1,024.
| Decimal unit | Bytes | Binary unit | Bytes |
|---|---|---|---|
| Kilobyte (kB) | 1,000 | Kibibyte (KiB) | 1,024 |
| Megabyte (MB) | 1,000,000 | Mebibyte (MiB) | 1,048,576 |
| Gigabyte (GB) | 1,000,000,000 | Gibibyte (GiB) | 1,073,741,824 |
| Terabyte (TB) | 1,000,000,000,000 | Tebibyte (TiB) | 1,099,511,627,776 |
| Petabyte (PB) | 1,000,000,000,000,000 | Pebibyte (PiB) | 1,125,899,906,842,624 |
That difference is why a "500 GB" drive holds 500,000,000,000 bytes, which is about 465.7 GiB, and a "1 TB" drive holds about 931.3 GiB. Windows counts in binary units but labels them GB, so it shows about 931 GB for a 1 TB drive. macOS and iOS report capacity in decimal units, so the same drive shows as 1 TB.
Bits vs. bytes: 1 byte = 8 bits
Internet speeds use bits per second: 100 Mbps = 100 / 8 = 12.5 MB/s
The 12.5 MB/s figure is the theoretical maximum, and real downloads are usually slower. Our Data Storage Converter switches between decimal and binary units.
Common Conversions for Everyday Life
| Scenario | Conversion |
|---|---|
| Height: 5'10" in metric | 177.8 cm (1.778 m) |
| Weight: 160 lb in metric | 72.6 kg |
| Driving: 65 mph in metric | 104.6 km/h |
| Oven: 375°F in Celsius | 190.6°C |
| Weather: 30°C in Fahrenheit | 86°F |
| Cooking: 2 cups in mL | 473 mL |
| Fuel economy: 30 mpg (US) in L/100 km | 7.84 L/100 km |
For other values, pick a category in the Unit Converter, enter a number and see the conversions at once. You can find more calculators in our converters hub.
Frequently Asked Questions
Why do the US and other countries use different measurement systems?
The metric system was developed in France in the 1790s and is now the basis of the international SI. The United States kept customary units in everyday use, although the customary units are themselves defined by metric values: since 1959 the yard has been exactly 0.9144 m and the pound exactly 0.45359237 kg. Under a 1988 amendment to the Metric Conversion Act of 1975, the metric system is the preferred system for US trade and commerce, and federal agencies are directed to use it in procurement and other business activities where practical, but customary units remain in wide everyday use. The UK is a mix: miles on road signs and pints for draught beer and cider remain legal imperial uses.
What is the difference between a US gallon and a UK gallon?
A US gallon is 3.785412 liters and an imperial (UK) gallon is 4.54609 liters, about 20% larger. The same gap applies to smaller units: an imperial pint is 568 mL and a US liquid pint is 473 mL. When you follow a recipe, check which country's measurements it uses.
How do I convert miles per gallon to liters per 100 km?
Divide 235.215 by the mpg value for US gallons. So 30 mpg is 235.215 ÷ 30 = 7.84 L/100 km, and 40 mpg is 5.88 L/100 km. Higher mpg means lower L/100 km because the two are inversely related. For imperial (UK) mpg, divide 282.481 by the mpg value instead, so 30 imperial mpg is 9.42 L/100 km.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature and multiply by 5/9. For example, 68°F is (68 - 32) × 5/9 = 20°C, and 350°F is (350 - 32) × 5/9 = 176.7°C. For a quick estimate, subtract 30 and halve, which is close near room temperature.
Why is my hard drive smaller than advertised?
Manufacturers count in decimal units, so 1 TB is 1,000,000,000,000 bytes. Windows divides by binary units (1,073,741,824 bytes per GB) but still labels the result GB, so it shows about 931 GB. No storage is missing. It is two ways of counting the same bytes.
Sources
- NIST. Special Publication 811: Guide for the Use of the International System of Units (SI), Appendix B (conversion factors, the 1959 yard and pound definitions, fuel economy conversion, and US metric law).
- NIST. Prefixes for binary multiples (kibi, mebi, gibi and the 1,024 step).
- Apple Support. How macOS and iOS report storage capacity.
- UK legislation. The Units of Measurement Regulations 1995 (imperial units still permitted for road signs, draught beer and cider, and a few other uses).
All sources were checked in September 2026.