The danger with metric-based systems is losing track of the decimal point. I did this during my A-level physics practical and the invigilator, who was wandering round making sure nobody was using a crafty AVOmeter, glanced at my pad and murmured "you might want to check that" as he passed my bench.

Indeed. We (structural engineers) measure on site to mm, but work out loads in kN/m

^{2} or kN/m. Steel section serial sizes are related to the dimension in mm, but the tables of section properties quote Z in cm

^{3} and I in cm

^{4} (zenzizenzic centimetres, FYI). Yield strengths of steels are quoted in MPa (N/mm

^{2} or 10

^{3}kN/m

^{2}). Young's modulus is quoted in GPa (kN/mm

^{2}).