Hi there, I now lost 16 Kg, but I don't think the NHS BMI Calculator takes muscle mass into account. When I measured my muscle mass with 3 professional scales I have got 40% muscle mass. This is way above average, and justified, as I have a very physically demanding job. Muscles are denser as they contain less water than fat, so it matters a great deal when the NHS BMI Calculator only gives me the option to enter "moderate" activity! Does anybody know a more accurate calculator?