Altra to La Sportiva shoe size

The short answer

Altra 8 is La Sportiva 39.5 by the two brands' own charts.

At least one of the two brands publishes no foot length, so the rows line up the US size both charts print. Treat it as the label conversion, not a fit.

Every Altra size read across to La Sportiva. US women's sizes on the left, EU on the right.
Altra	Altra builds it for	La Sportiva, by chart	Same label	La Sportiva builds it for	La Sportiva also prints
4	foot length 20.5 cm	not made	not published	not published	not published
4.5	foot length 21 cm	not made	not published	not published	not published
5	foot length 21.5 cm	not made	not published	not published	not published
5.5	foot length 22 cm	36	not published	not published	US women's 5.5 · US men's 4.5
6	foot length 22.5 cm	37	not published	not published	US women's 6 · US men's 5
6.5	foot length 23 cm	37.5	not published	not published	US women's 6.5 · US men's 5.5
7	foot length 23.5 cm	38	not published	not published	US women's 7 · US men's 6
7.5	foot length 24 cm	38.5	not published	not published	US women's 7.5 · US men's 6.5
8	foot length 24.5 cm	39.5	not published	not published	US women's 8 · US men's 7
8.5	foot length 25 cm	40	not published	not published	US women's 8.5 · US men's 7.5
9	foot length 25.5 cm	40.5	not published	not published	US women's 9 · US men's 8
9.5	foot length 26 cm	41	not published	not published	US women's 9.5 · US men's 8.5
10	foot length 26.5 cm	42	not published	not published	US women's 10 · US men's 9
10.5	foot length 27 cm	42.5	not published	not published	US women's 10.5 · US men's 9.5
11	foot length 27.5 cm	43	not published	not published	US women's 11 · US men's 10
11.5	foot length 28 cm	not made	not published	not published	not published
12	foot length 28.5 cm	not made	not published	not published	not published
13	foot length 29.5 cm	not made	not published	not published	not published

Tinted rows change label or sit between two sizes. 6 sizes have no counterpart on the La Sportiva chart. Read from the two charts only; no formula and no averaging.

What wearers say

Charts describe a garment. People who own both brands describe a fit, and their answer ranks above this table once five of them stand behind it. Pick your size in the converter to see whether there are enough yet.

Open in the converter Add an item you own

Sources

Altra size guide, read on 2026-09-17. Altra on TrueToSize
La Sportiva size guide, read on 2026-09-17. La Sportiva on TrueToSize

La Sportiva to Altra