This heading has a font size of 72pt. This means that it should have a height of 1 inch = 2.54cm when printed.
This heading has a font size of 2.54cm. This means that it should have the same size as the previous heading when printed (2.54cm as well).
The height should in both cases at least roughly (only roughly!) be measured from the "highest ascender" (the "h") to the "lowest descender" (the "g").