How about 5ft7 vs 170cm. The later seems easier to express to me. If only rough accuracy is required then you only really need to take note of the first two digits. Incidentally converting between the two is quite messy; first you must learn that 1ft = 12 inches, then multiply the 5 by 12 then add 7 then multiply by 2.54. Where as to convert a metric figure to imperial, it does not matter so much whether you are starting out in metres or centimetres.