If I 11 Stone 11lbs How Much Do I Weigh In Kilos?

First let us convert your weight into pounds so that we have one unit to work with.
One stone is equal to 14 pounds. So, if you weigh 11 stone 11 lbs, your weight in pounds would be:

Weight in lbs = 11 (14) + 11
  = 154 +11
  = 165 lbs

So, your weight in pounds is 165 lbs.

Now, every kilogram has about 2.2 pounds to it.
Therefore, if you weigh 165 lbs:

Kg : Lbs
1   : 2.2
x   : 165

2.2x = 165
x = 75 kg

So, you weight in kilograms is:

75kg