315 is the section width in millimeters. 75 is the aspect ratio; the sidewall height is 75% of the section width. and 16 is the wheel diameter.
Divide with by 25.4 to get width in inches
315/25.4 ~ 12.4 inches
Multiply width by aspect ratio to get sidewall height.
12.4*.75= 9.3 inches
To get the height multiply the sidewall height by 2 (to account for the sidewall on each side of the wheel) and add the wheel height
77 CJ-7- AMC 360, Edelbrock cam, MC2100, Fenderwells, CJ T18/D20, Chevy D44/EB 9" rear, Trutrac f/r, 4.11, SOA, 1.25 lift shackles, 35x12.50 BFG KM2s, Shackle Reversal