Here's how to convert 11 and a half stone to kilos:

* Stone to Pounds: One stone is equal to 14 pounds.

* 11.5 Stone to Pounds: 11.5 stones * 14 pounds/stone = 161 pounds

* Pounds to Kilograms: One pound is equal to 0.453592 kilograms.

* 161 Pounds to Kilograms: 161 pounds * 0.453592 kg/pound = 73.03 kilograms

Therefore, 11 and a half stone is approximately 73.03 kilograms.