Hundredweight (UK) to Kilograms (cwt (UK) to kg)

1 hundredweight (UK) equals 50.80234544 kilograms exactly.

1 hundredweight (UK) = 50.80234544 kilograms

How to convert hundredweight (UK) to kilograms

To convert hundredweight (UK) to kilograms, multiply the number of hundredweight (UK) by 50.80234544. This factor is exact. To go the other way, multiply kilograms by 0.01968413055 (rounded).

kilograms = hundredweight (UK) × 50.80234544

Example: 10 hundredweight (UK) = 508.0234544 kilograms.

About these units

Hundredweight (UK) (cwt (UK))

Imperial (British)Traditional unit (still used in some regions)

112 pounds (50.80 kg), eight stone. Twenty of them make a long ton.

Hundredweight, abbreviated cwt, comes from the medieval Latin centum for a hundred, though the English hundred around 1300 varied in size. The Weights and Measures Act 1835 fixed the imperial unit at 112 pounds, which is 8 stone, or about 50.80 kilograms. NIST gives the factor as 50.80235 kilograms and does not mark it as exact.

A rival 100 pound version crossed the Atlantic and was used in the United States and Canada. Britain banned it in 1824 over fraud fears, then legalised it in 1879 as the cental after merchants importing American wheat and tobacco pressed for it. Twenty long hundredweight make a 2,240 pound ton. The unit measured cattle, fodder, fertiliser and coal, and old anvils and church bells carry weights stamped in hundredweight, quarters and pounds. Guernsey and older van and truck ratings still use it.

1 hundredweight (UK) = 50.80234544 kilograms (exactly).

Sources: Wikipedia: Hundredweight; NIST SP 811, Appendix B.8 conversion factors

Kilogram (kg)

Metric (SI)Current unit

The SI base unit of mass. Since 2019 it is defined by fixing the value of the Planck constant, replacing the old platinum-iridium cylinder in Paris.

Oddly for a base unit, the kilogram began life as a derived one. In 1793 revolutionary France defined the grave as the mass of one litre of water, and a decree of 1795 then replaced it with the kilogramme, a name built from the Greek khilioi (a thousand) and gramma, a Late Latin word for a small weight. In 1799 a platinum cylinder, the Kilogramme des Archives, became the physical standard, matching a cubic decimetre of water at its densest, around 4 degrees Celsius. In 1889 the metric community adopted a platinum-iridium cylinder made in 1879, the International Prototype of the Kilogram, nicknamed Le Grand K.

The kilogram is still the only SI base unit with a prefix in its name. Because SI forbids stacked prefixes, a millionth of a kilogram is a milligram rather than a microkilogram, so every mass prefix is attached to the gram. Calibrating every national standard against one object in a vault near Paris meant that all of them drifted relative to it, so in November 2018 member states voted to tie the kilogram to a fixed value of the Planck constant. The change took effect on 20 May 2019. Day to day nothing shifted, but the definition no longer depends on a single piece of metal.

The kilogram is the reference unit for weight & mass on this site.

Sources: NIST: Kilogram introduction (SI redefinition); Wikipedia: Kilogram

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