Altra to norda shoe size

The short answer

Altra 5.5 is norda 6 by the two brands' own charts. 10 of 10 Altra sizes land on a different label at norda.

Both brands publish the foot length each size is built for, so every row matches a foot, not a label.

On 1 sizes the charts land two or more sizes from the same label. Brands do not measure the body the same way, so on those rows treat the chart answer and the same label as the two ends of a range.

Every Altra size read across to norda. US women's sizes on the left, US women's on the right.
Altra	Altra builds it for	norda, by chart	Same label	norda builds it for	norda 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	6	not published	foot length 22 cm	UK 3.5 · EU 36 · CM / JP 23
6	foot length 22.5 cm	6.5	6	foot length 22.5 cm	UK 4 · EU 36 2/3 · CM / JP 23.5
6.5	foot length 23 cm	7	6.5	foot length 23 cm	UK 4.5 · EU 37 1/3 · CM / JP 24
7	foot length 23.5 cm	7.5	7	foot length 23.5 cm	UK 5 · EU 38 · CM / JP 24.5
7.5	foot length 24 cm	8	7.5	foot length 24 cm	UK 5.5 · EU 38 2/3 · CM / JP 25
8	foot length 24.5 cm	8.5	8	foot length 24.5 cm	UK 6 · EU 39 1/3 · CM / JP 25.25
8.5	foot length 25 cm	9	8.5	foot length 25 cm	UK 6.5 · EU 40 · CM / JP 25.5
9	foot length 25.5 cm	9.5 or 10	9	foot length 25.3 cm	UK 7 · EU 40 2/3 · CM / JP 26
9.5	foot length 26 cm	10 or 10.5	9.5	foot length 25.8 cm	UK 7.5 · EU 41 1/3 · CM / JP 26.5
10	foot length 26.5 cm	11	10	foot length 26.5 cm	UK 8.5 · EU 42 2/3 · CM / JP 27.5
10.5	foot length 27 cm	not made	10.5	not published	not published
11	foot length 27.5 cm	not made	11	not published	not published
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. 8 sizes have no counterpart on the norda 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.

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Sources

Altra size guide, read on 2026-09-17. Altra on TrueToSize
norda size guide, read on 2026-09-18.

norda to Altra