235s are roughly the same height as 7.50s, maybe a cm or so taller depending on make - but they are a lot fatter, several inches wider.
The maths is that 7.50s are "square" - 7.50 in high and 7.50 in wide. The Metric 235/85s are 235mm wide and 85% of that high so...
235mm = roughly 9.5 inches wide.
235mm x 0.85 ratio = 20 Cm high or roughly 8 inches high.
( checked against the 7.50 General Super All Grips on the lightweight and the 235/85 Michelin Scorpion Muds on the 90)