Family Stem Weights Calculator Version 4.0

Thin

Black

Steps

Decimals?

Equal Steps

Impallari Formula

Luc(as) Formula

Styles

Equal Steps

Impallari Formula

Luc(as) Formula

Step 1

20

20

20

Step 2

+25 45

+9 29

+7 27

Step 3

+25 70

+16 45

+9 36

Step 4

+25 95

+21 66

+13 49

Step 5

+25 120

+27 93

+17 66

Step 6

+25 145

+31 124

+24 90

Step 7

+25 170

+34 158

+31 121

Step 8

+25 195

+33 191

+42 163

Step 9

+25 220

+29 220

+57 220

My formula describes an Ogee Curve in between the Lucas Theory and Equal steps.
This seems to be the most useful pattern to distribute weight across a font family.
Especially in large families with many weights, or where the Black-Thin difference is lengthy.

You can take this values as a pretty good starting point, and then refine acording to your eyes.
Cheers, Pablo Impallari.

Reference:
Luc(as) de Groot’s Interpolation Theory
Weight interpolation and maths
Golden Section as a method for finding regular and bold complements
Using Multiple Masters to Generate Weights in a Family - Insight?
Font weights and font weight scaling
CSS Fonts Module Level 3 - font-weight property

Discuss, suggest changes and improvements:
Project Page, Typophile and TypeDrawers

More Impallari Tools:
Drag and Drop Font Testing page
Simplepolator
Spacing Macro