To calculate your exact BMI marker, go here --> Click me.
Anything between 18.5 and 24.9 is healthy. Anything above or below is not...
...which is complete bollocks. Why the army rely on the BMI index is beyond me. People who do lots of exercise (Because muscle is a lot heavier than fat) often have skewered results resulting in completely inaccurate gradings.
Which describes about 99% of the people trying to join the british army then.