Weight: how thick the main stem is

How font.io measures font weight — the width of the capital H's stem as a share of the font's size, from thin to black.

Archivo Black: 0.22 of the font’s size — black. Inter Regular: 0.09 — medium. Weight is the thickness of a letter’s main upright stroke, measured as a share of the font’s full size. We sort it into six buckets: thin, light, regular, medium, bold, black.

Weight: measuring the stem

Archivo Black ‘H’ — calipers span the left stem at the three sample heights measure.py uses (20%, 25%, 30% of the ink height, above the crossbar)

Median of the three samples ÷ em = the weight ratio. Boundaries: thin <0.040, light <0.055, regular <0.090, medium <0.110, bold <0.140, else black. This outline-based pass agrees with measure.py to the third decimal.

The measurement is deliberately simple. Take the capital H, slice across it at three heights, and measure the width of the left stem each time. Take the middle of the three values — the median, so a serif or a flare at one height can’t skew it — and divide by the font’s size.

Why measure it ourselves instead of reading the font’s own weight label? Because the label sometimes lies. Plenty of free fonts claim to be weight 500 or 700 in their metadata while the actual stems tell a different story. The outlines don’t lie.

A real example: Archivo Black’s H stem measures 0.220 — black. Inter Regular’s measures 0.0925 — medium.

One caveat: hollow and inline faces get flagged, not silently scored. On an inline face the “stem” the slicer finds is the thin inline stroke, so the number would describe the decoration instead of the letter — we mark it and move on.