Unit Converter — Length, Weight & Temp

This unit converter handles 19 categories, including length, weight, area, volume, temperature, speed, pressure, data size and fuel economy. Everyday conversions such as inches to cm, lbs to kg and Fahrenheit to Celsius sit next to specialist units like psi, kgf/cm², GiB and mpg. Enter one value and the page lists it in every unit of the category at once, so you do not need a separate conversion chart. Factors use the exact international definitions rather than rounded approximations.

How to use

1. Choose a category from the buttons at the top, or from the "Category" list on a phone, such as Length, Weight and mass or Temperature.
2. Type a number in "Value to convert". Decimals and negative numbers are accepted.
3. Choose the "From" and "To" units. The result appears in large type with a line such as 1 in = 2.54 cm underneath, and an "Exact by definition" badge when the factor is exact.
4. Press the ⇄ button ("Swap units") to reverse the direction; the result you just got becomes the new value to convert.
5. Read the "In every unit" table to see the value in every unit of the category. Select a row to make that unit the "To" unit.
6. Under "Display", pick "Significant digits" or "Decimal places" and set "Digits". Then use "Copy value" for the number or "Copy link" for an address that reopens this exact category, unit pair and value.

How it works

• Factors follow NIST SP 811, the 1959 international yard and pound agreement and the SI. 1 in = 25.4 mm, 1 lb = 0.45359237 kg and 1 US gal = 3.785411784 L are exact, not rounded.
• Very large or very small values are shown in scientific notation; 1.5E-7 means 1.5 × 10⁻⁷.
• Korean traditional units are included: 1 ja = 10/33 m, 1 pyeong = 400/121 m², 1 don = 3.75 g, 1 geun = 600 g for meat and 1 doe ≈ 1.8039 L. The ri varied by region and period, so treat it as approximate.
• The plain calorie (cal) is the thermochemical calorie, 4.184 J; food Calories are kilocalories. Months and years in the Time category are Gregorian averages (1 year = 365.2425 days).
• Everything runs in the browser and nothing you type is uploaded. Your last category, units, value and display setting are saved on this device.

Inches to cm and lbs to kg: formulas with worked examples

One inch is exactly 2.54 cm and one pound is exactly 0.45359237 kg, because the 1959 international agreement defined them that way. A 27-inch monitor has a 27 × 2.54 = 68.58 cm diagonal, a height of 5 ft 11 in is 71 inches or 180.34 cm, and 70 kg is 70 ÷ 0.45359237 ≈ 154.32 lb.

Temperature cannot be converted with a single multiplication. Use °C = (°F − 32) × 5 ÷ 9, or °F = °C × 9 ÷ 5 + 32 for the other direction. 100 °F is about 37.78 °C, 25 °C is 77 °F, and the two scales meet at −40. For that reason the Temperature category does not show a one-unit factor line.

GB vs GiB: why a 1 TB drive shows about 931 GB

Drive makers count 1 TB as 1,000,000,000,000 bytes (SI), while many operating systems count in binary steps of 1024. Dividing a trillion bytes by 1024³ gives about 931.32, which is why a new 1 TB drive appears as roughly 931 GB; the system's GB label really means GiB. A 500 GB drive is about 465.66 GiB.

Internet speeds in Mbps are megabits per second, while file sizes in MB are megabytes. Eight bits make a byte, so a 500 Mbps connection tops out at 62.5 MB per second in theory. The Data size and Data rate categories keep bits, bytes and binary units apart.

Tire pressure psi to bar and mpg to L/100 km

One psi is about 6,894.757 Pa. A typical car tire pressure of 32 psi is about 2.206 bar or 2.250 kgf/cm². Bar and kgf/cm² look close, but 1 kgf/cm² is 0.980665 bar, about 2% less, so check which unit the manual uses before converting.

Fuel economy units are reciprocal. 30 mpg (US) is about 12.75 km/L, or about 7.84 L/100 km, and for L/100 km a smaller number means better economy. A UK gallon is about 20% larger than a US gallon, so the same car shows a higher mpg figure in the UK than in the US.

Cups, tablespoons and fluid ounces for cooking

The US cup here is one sixteenth of a US gallon, 236.5882365 mL; a US tablespoon is 14.79 mL, a US teaspoon 4.93 mL and a US fluid ounce 29.57 mL. Metric recipe cups are often 250 mL and the cups in Korean recipes are often 200 mL, so a cup is not one fixed size worldwide. When a recipe comes from another country, converting to millilitres first avoids the mismatch.

Questions and answers

How many centimeters are in an inch?

Exactly 2.54 cm. So 27 inches is 27 × 2.54 = 68.58 cm.

How do I convert Fahrenheit to Celsius?

°C = (°F − 32) × 5 ÷ 9. 100 °F is about 37.78 °C. To go the other way, °F = °C × 9 ÷ 5 + 32.

How many kilograms are in a pound?

Exactly 0.45359237 kg, or about 0.454 kg. One kilogram is about 2.2046 pounds.

How many megabytes per second is 100 Mbps?

12.5 MB per second in theory. There are 8 bits in a byte, so divide by 8; the "Data rate" category converts this directly.

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

The maker counts in thousands and the operating system in 1024s. 1 TB is about 931.32 GiB, so no space is missing.

How many square feet are in a square meter?

About 10.764 square feet. One square foot is exactly 0.09290304 m².

What is 32 psi in bar?

About 2.206 bar. That is about 2.250 kgf/cm², and the "Pressure" category shows psi, bar, kPa and kgf/cm² side by side.

What is the difference between a US gallon and a UK gallon?

A US gallon is 3.785411784 L and a UK gallon is 4.54609 L, so the UK gallon is about 1.2 times larger. US and UK fluid ounces and pints also differ.

How many grams are in a troy ounce?

Exactly 31.1034768 g. A regular (avoirdupois) ounce used for food is 28.349523125 g, about 10% lighter.