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Common Unit Conversions

Quick-reference factors for length, weight, speed, and area — plus why temperature is the one category that doesn't play by the same rules.

Length

Length conversions use a fixed multiplication factor, since all length units share the same zero point.

1 mile = 1.609 km
1 km = 0.621 mi
1 yard = 0.9144 m
1 foot = 0.3048 m
1 inch = 2.54 cm

Weight

1 kg = 2.205 lb
1 lb = 0.4536 kg
1 oz = 28.35 g
1 metric ton = 1,000 kg
1 US ton = 907.18 kg

Temperature — the odd one out

Unlike length or weight, Celsius, Fahrenheit, and Kelvin don't share a common zero point. Water freezes at 0°C, 32°F, and 273.15K — three different numbers for the same physical state. That means converting temperature requires an offset formula, not just a multiplication factor:

°F = (°C × 9/5) + 32 °C = (°F − 32) × 5/9 K = °C + 273.15

This is why you can't simply scale a temperature the way you'd scale a length — multiplying 0°C by any factor still gives 0, but 0°C clearly isn't "no temperature."

Speed

1 m/s = 3.6 km/h
1 mph = 1.609 km/h
1 knot = 1.852 km/h
1 km/h = 0.621 mph

Area

1 acre = 4,046.86 m²
1 hectare = 10,000 m²
1 sq mile = 2.59 km²
1 sq foot = 0.0929 m²

A note on US vs. UK units

Some unit names are shared between systems but defined slightly differently by historical convention. The most common trap: "ton" means 2,000 pounds in the US (short ton) but 2,240 pounds in the UK (long ton) — neither of which matches the 1,000-kilogram metric ton used almost everywhere else. Similar quirks exist for gallons and pints, where US and UK (imperial) definitions diverge. When precision matters, it's worth double-checking which system a source is using.

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Our unit converter covers length, weight, temperature, speed, and area, using these same standard conversion factors, with results shown to six decimal places.

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Frequently asked questions

Celsius, Fahrenheit, and Kelvin don't share a common zero point, so converting between them requires an offset formula rather than a simple multiplication factor used for length or weight.

A metric ton equals 1,000 kilograms (about 2,204.6 lb). A US short ton equals 2,000 pounds, roughly 907.18 kg — noticeably lighter than a metric ton.

Some unit names are shared but defined differently by historical convention — most notably "ton" (UK long ton vs. US short ton) and certain volume units like gallons and pints, where US and UK (imperial) definitions diverge.

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