Why Cup Size Is Relative To Band Size

   For those of you with a scientific bent of mind, this snippet from Wikipedia will explain why these cups have the same size: 38A = 36B = 34C = 32D = 30DD = 28E
and why each of these cups is bigger that the precedent: 28C < 30C < 32C < 34C < 38C

    Cups give a hemi sperical shape to breasts and underwires give shape to cups. So the curvature radius of the underwire is the key parameter to determine volume and weight of the breast. The same underwire are used for the cup of size 36A, 34B, 32C, 30D and etc... so those cup have the same volume. The reference number of underwire size are based on B cup bra, for example underwire size 32 is for 32B cup (and 34A, 30C...). An underwire size 30 with has a curvature diameter of 3 inch 5/6 ≈ 9.7 cm and this diameter increase of ⅓ inch ≈ 0.847 cm by size. The table below is fill with all the size that can be find in ready to wear large size shop

Underwire sizeBra sizeCup diameter Volume of one cupWeight of both breasts
3032A 30B9.7 cm (3 in 5/6)240 cc (0.51 US pt)0.43 kg (0.95 lb)
3234A 32B 30C10.6 cm (4 in 1/6)310 cc (0.66 US pt)0.56 kg (1.2 lb)
3436A 34B 32C 30D11.4 cm (4 in 1/2)390 cc (0.82 US pt)0.70 kg (1.5 lb)
3638A 36B 34C 32D 30E12.3 cm (4 in 5/6)480 cc (1.0 US pt)0.86 kg (1.9 lb)
3840A 38B 36C 34D 32E 30F13.1 cm (5 in 1/6)590 cc (1.2 US pt)1.1 kg (2.4 lb)
4042A 40B 38C 36D 34E 32F 30G14.0 cm (5 in 1/2)710 cc (1.5 US pt)1.3 kg (2.9 lb)
4244A 42B 40C 38D 36E 34F 32G 30H14.8 cm (5 in 5/6)850 cc (1.8 US pt)1.5 kg (3.3 lb)
4446A 44B 42C 40D 38E 36F 34G 32H 30I15.7 cm (6 in 1/6)1,000 cc (2.1 US pt)1.8 kg (4.0 lb)
4648A 46B 44C 42D 40E 38F 36G 34H 32I 30J16.5 cm (6 in 1/2)1,180 cc (2.5 US pt)2.1 kg (4.6 lb)
4850A 48B 46C 44D 42E 40F 38G 36H 34I 32J 30K17.4 cm (6 in 5/6)1,370 cc (2.9 US pt)2.5 kg (5.5 lb)
5052A 50B 48C 46D 44E 42F 40G 38H 36I 34J 32K18.2 cm (7 in 1/6)1,580 cc (3.3 US pt)2.8 kg (6.2 lb)
5252B 50C 48D 46E 44F 42G 40H 38I 36J 34K 32L19.0 cm (7 in 1/2)1,810 cc (3.8 US pt)3.3 kg (7.3 lb)
5454B 52C 50D 48E 46F 44G 42H 40I 38J 36K 34L 32M19.9 cm (7 in 5/6)2,060 cc (4.4 US pt)3.7 kg (8.2 lb)
5656B 54C 52D 50E 48F 46G 44H 42I 40J 38K 36L 34M 32N20.7 cm (8 in 1/6)2,340 cc (4.9 US pt)4.2 kg (9.3 lb)
5858B 56C 54D 52E 50F 48G 46H 44I 42J 40K 38L 36M 34N21.6 cm (8 in 1/2)2,640 cc (5.6 US pt)4.8 kg (11 lb)
6058C 56D 54E 52F 50G 48H 46I 44J 42K 40L 38M 36N22.4 cm (8 in 5/6)3,000 cc (6.3 US pt)5.3 kg (12 lb)


Check these out: