Letter to FR clothing size

The short answer

By the formula, Letter XS is FR 32 to 34. On brand charts the most common answer is 34 (3 of 3 brands), and 3 different answers are in print.

The formula and the brands' most common answer differ on 5 of 7 sizes below. Use the brand's own number for the brand you are buying.

Letter to FR. The formula column is arithmetic; the brand columns are read from 3 brand charts checked by hand.
Letter	FR by formula	Most brands print	Other answers in print
XXS	30	not published	not published
XS	32 to 34	34 (3 of 3)	32: J.Crew; 36: Reiss
S	36 to 38	36 (2 of 3)	38: J.Crew, Reiss; 40: Reiss
M	40 to 42	42 (2 of 3)	38: Sandro; 40: J.Crew; 44: Reiss
L	44 to 46	46 (2 of 3)	40: Sandro; 44: J.Crew; 48: Reiss
XL	48 to 50	42 (1 of 2)	48: J.Crew
XXL	52 to 54	not published	not published

Tinted rows: the formula differs from the brands' most common answer. A brand is counted once per answer.

The widest split is at Letter L: brand charts print anything from FR 40 to 48 for the same size.