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 1⁄60) 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.
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 √m.