Metric foot

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For the poetical term, see foot (prosody).

A metric foot is a nickname occasionally used in the United Kingdom for a length of 300 millimetres (30 cm).

The 30 cm metric ruler was of a similar length to the traditional 12-inch (one foot) ruler, so hence the term 'metric foot'. A metric foot can be divided into twelve "metric inches" of 25 millimetres (2.5 cm) each. The (short) metric foot and inch are therefore 4.8 and 0.4 millimetres (or about 160) shorter than an imperial foot and inch respectively.

The term "metric foot" does not appear in any British Standard, but the construction industry uses multiples of 300 mm and 600 mm as preferred dimensions as per the international standard on modular coordination, ISO 2848. These numbers were chosen because of their large number of divisors - any multiple of 600 mm can be evenly divided into 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 25, 30, etc. parts.

While the term "metric foot" is still occasionally used in the United Kingdom, in particular in the timber trade, dimensions are most likely to be quoted exclusively in metric units today.

The sizes of the studios at BBC Television Centre in London, which opened in 1960, are specified and measured in metric feet—a contrast to film stages where imperial feet and inches prevail.

Historically in France, under the mesures usuelles system (intermediary between traditional French units and metric units), a (long) metric foot was exactly a third of a metre (333 13 mm).

As metric utilizes a powers of 10 motif, one approach to the metric foot is to set it as the geometric mean of the two above usages (30cm & 1/3m), or the 110m.

The following compares the relative lengths of the short metric foot (smf), the imperial foot, the geometric mean metric foot (mf), and the long metric foot (lmf), left to right, respectively.
Comparison of three versions of the metric foot with the imperial foot. Leftmost line represents 30cm (the short metric foot), next is the imperial foot (0.3048 m), next the geometric mean metric foot (mf) (sqrt(1/10)m), and rightmost is 1/3 m (the long metric foot).

See also[edit]

Further reading[edit]