calculate typo line gap

[af209]

can you correct me please,

if units per em is 2048.
Typo Line Gap value between 7%

so, 2048-7%= 1904.64
then the Typo Line Gap value is 2048 - 1904=144. so the value of typo line gap is 144.

are im right?

[Erwin Denissen]

if units per em is 2048.
Typo Line Gap value between 7%

In your case 7% of upem is 0.07 * 2048 = 143.36 = 143.

But all metrics should be in balance. If the outlines are too small or too large, you should consider increasing or reducing the size of your glyph outlines. We consider outlines too small if the CapHeight is less than ½ upem, and it is too large if is exceeds ¾ upem.

It might be wise to open some other fonts and see how their metrics fit together.