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Why Unit Conversion Matters
Whether you’re cooking with a recipe from another country, traveling abroad, or working on an engineering project, converting between measurement units is something most of us need to do regularly.
Common Length Conversions
The most frequently needed length conversions:
| From | To | Formula |
|---|---|---|
| Inches | Centimeters | × 2.54 |
| Feet | Meters | × 0.3048 |
| Miles | Kilometers | × 1.609 |
| Centimeters | Inches | × 0.3937 |
| Meters | Feet | × 3.281 |
| Kilometers | Miles | × 0.6214 |
Example: Convert 5’10” to Centimeters
| Note | Result |
|---|---|
| height = 5 feet + 10 inches | 5 feet 10 inches |
| height in cm | 177.80 cm |
Common Weight Conversions
| From | To | Formula |
|---|---|---|
| Pounds | Kilograms | × 0.4536 |
| Kilograms | Pounds | × 2.205 |
| Ounces | Grams | × 28.35 |
| Stones | Kilograms | × 6.35 |
Example: Convert 150 lbs to kg
150 × 0.4536 = 68.04 kg
Temperature Conversions
Temperature conversions use different formulas than simple multiplication:
- Celsius to Fahrenheit:
°F = (°C × 9/5) + 32 - Fahrenheit to Celsius:
°C = (°F - 32) × 5/9 - Celsius to Kelvin:
K = °C + 273.15
Example: Convert 72°F to Celsius
°C = (72 - 32) × 5/9
°C = 40 × 5/9
°C ≈ 22.2°C
Volume Conversions
| From | To | Formula |
|---|---|---|
| Gallons | Liters | × 3.785 |
| Liters | Gallons | × 0.2642 |
| Cups | Milliliters | × 236.6 |
| Fluid ounces | Milliliters | × 29.57 |
Free Unit Converter
Convert between length, weight, temperature, and volume units instantly. Need a specific pair, like kilometers to miles or psi to bar? Every pair has its own page in the unit converters index.
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Frequently Asked Questions
How do you convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8), then add 32. The formula is: F = (C x 9/5) + 32. For example, 25 degrees Celsius = (25 x 1.8) + 32 = 77 degrees Fahrenheit.
How many centimeters are in an inch?
One inch equals exactly 2.54 centimeters. To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54 (or multiply by 0.3937).
How do you convert pounds to kilograms?
Multiply the weight in pounds by 0.4536 to get kilograms. For example, 150 pounds = 150 x 0.4536 = 68.04 kilograms. To convert back, multiply kilograms by 2.205.
Convert Units in Notes Calculator
Notes Calculator has built-in conversion for 250+ units. Just use to, in, or as between units:
| Note | Result |
|---|---|
| 10 inches in cm | 25.40 cm |
| 26.2 miles in km | 42.16 km |
| # Weight | |
| 150 pounds to kg | 68.04 kg |
| 250 grams in ounces | 8.82 oz |
| # Temperature | |
| 72 fahrenheit to celsius | 22.22 °C |
| 0 celsius in fahrenheit | 32 °F |
| # Volume | |
| 2 US gallons in liters | 7.57 L |
| 2 imperial gallons in liters | 9.09 L |
| 500 ml in liters | 0.50 L |
The app supports lengths, weights, temperatures, volumes, speeds, pressures, digital data (bytes, megabytes), areas, electrical units, data rates, and even shoe sizes. You can also mix units in arithmetic: 5 km + 300 m shows 5.30 km, in the larger unit, and 63 inches shows 5 feet 3 inches. For square feet, acres, and hectares, the area calculator covers room and land measurements. For currencies, type 100 USD in EUR to convert between 200+ currencies with live exchange rates. The converting units guide in the docs shows how to wrap a value in a unit and mix units in arithmetic.
If you convert units in the kitchen, our calculator for caterers and bakers shows how to scale a dough with baker’s percentages, turn grams into pounds, and work out how many bottles an event bar needs in the same notepad.
If you coach clients between kilos and pounds, our calculator for personal trainers and nutritionists shows how to convert plate weights, estimate a one-rep max, and split calories into macros in the same note.
If you measure in feet and inches but buy materials in metric, our calculator for contractors and tradespeople shows how to convert a drawing to millimeters, work out paint for two coats, and mark up parts for a quote in the same note.
If you work out mulch and seed from lawn and bed measurements, our calculator for landscapers and farmers shows how to turn areas into cubic yards of mulch, seed by the acre and a cost per acre in the same note.
Unit conversions come up frequently in health and fitness calculations like BMI, and on the bench. See the engineering unit converter workflow for drawings, material specs, and tolerance stack-ups in one notepad. For Mac users, see our guide on the best calculator apps for Mac that include built-in unit conversion.