US to FR clothing size

The short answer

By the formula, US 00 is FR 30. On brand charts the most common answer is 28 (1 of 2 brands), and 4 different answers are in print.

The formula and the brands' most common answer differ on 2 of 12 sizes below. Use the brand's own number for the brand you are buying.

US to FR. The formula column is arithmetic; the brand columns are read from 3 brand charts checked by hand.
US	FR by formula	Most brands print	Other answers in print
00	30	28 (1 of 2)	30: J.Crew; 32: J.Crew; 34: Reiss
0	32	28 (1 of 2)	30: J.Crew; 32: J.Crew; 34: Reiss
2	34	34 (2 of 3)	36: Reiss
4	36	36 (2 of 3)	38: Reiss
6	38	38 (2 of 3)	40: Reiss
8	40	40 (2 of 3)	42: Reiss
10	42	42 (2 of 3)	44: Reiss
12	44	44 (1 of 2)	46: Reiss
14	46	46 (1 of 2)	48: Reiss
16	48	not published	not published
18	50	not published	not published
20	52	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 US 00: brand charts print anything from FR 28 to 34 for the same size.