Doctors and Medical
If you go the Doctors and have your weight or height measured, it will usually be in metric. Although some medical places might quote you the sizes in non-metric units, some will quote in metric, and certainly all data is recorded in metric in the NHS.
It can be very helpful to know your height and weight in metric, as you can use these figures to easily calculate your Body Mass Index (BMI). BMI is calculated using the formula BMI = weight divided by height squared, i.e. kilograms divided by metres squared, e.g. 72 kg/(1.72 m × 1.72 m) = 24.3. More information can be found on our page on weight and mass.
When you visit the gym, they are likely to measure skin folds in millimetres and to calculate your body mass index using your mass in kilograms and your height in metres.