The below is a guide as to how to calculate your body mass index (BMI). This is an indicator as to how healthy you are. Note that my BMI used to be 25, right on the cusp of being overweight. As someone who was a size 10, that seemed a little far fetched to me, even though I'm short. So this is just a useful indicator.
Height centimetres: 160cm
Heigh in feet: 5
And inches: 3
Height in inches: 63
Body weight in pounds: 128
Body Mass Index = Body weight * 703 / Height in inches squared
e.g. Body Mass Index = ( 128 * 703 ) / 63 * 63
Body Mass Index = 22.7
This number doesn't actually mean anything unless you have a scale to compare it to. Below is the recognised scale for BMI:
12 - 18 BMI = underweight
18 - 24 BMI = healthy
25 - 29 BMI = Overweight (this is where I used to sit, at 25)
30 - 39 BMI = Obese
40 - 42 BMI = Extremely Obese
The ideal BMI for you should be between 18 - 24, however, depending upon your build will depend on whether this scale works for you. If you are a short, muscular man, I wouldn't be surprised if you came up on this scale as obese. Similarly, if you are a tall, lean woman, you may appear underweight on this scale.
When using BMI, I would recommend using the above scale in context to other measurements. These can be hip to waist ratio and body fat %.