Is arm span equal to height?

Roughly: for most adults arm span is within a few centimetres of height.

Human body proportions by height

Figures on the board use realistic adult proportions that change with height, sex and build. Common artist and anthropometry rules of thumb:

Proportion	Rule of thumb
Height in head lengths	about 7–8 heads for adults (4 for a toddler)
Arm span	roughly equal to height
Leg length (to crotch)	about half of total height
Shoulder width	about 2 head lengths (men), a little less for women
Eye level	about 93% of total height

Try it: add a person on the board, change the height, and watch the proportions and eye level update.