If you can add the dimensions, then I will edit this answer to actually be helpful.
He was 4 foot. With this I just took .5 and multiplyed it by 4, then subtracted it from 6. Hope this can help! Feel free to message me if you have anymore questions!
8.6x + 3 + 8.6+3 =. 17.2x + 6
5.2+5.2= 10.4
17.2x + 6 = 10.4
Hope this helps! This is how you do it.
Is there a chart because there is no reference..