How to Determine Bra Size

Underbust inches
Overbust inches

Women can measure bra size at home with a flexible tape measure and a little arithmetic. Bra sizes have two components: the band size and the cup size. In the US, the band size is an even number between 28 and 48, and the cup size is a letter A through D. Cup sizes smaller than A may be labeled AA, while cup sizes larger than D may be labeled E (DD), F (DDD), or G. Some brassiere manufacturers also make half cup sizes, such as AB, BC, and CD. To calculate your correct bra size, follow this simple procedure, or use the bra size calculator at left.

Band Size

Place the tape measure around your midsection, just below your breasts. This is called the underbust measure. Round the measurement to the nearest even number. For example, if your underbust measurement is 33.5 inches, round it to 34. If your underbust measurement is 36.5, round it to 36. If your underbust measurement is 35, you can either round it up to 36 or down to 34; conventionally, women round down.

Cup Size

Measure around your breasts at their fullest part (across the nipples). This is called the overbust measure. Subtract the underbust from the overbust, and round the difference up to the nearest integer. Cup size is determined as follows: 1" = A, 2" = B, 3" = c, 4" = D, etc.

Example: Mary has an underbust measure of 33.5 inches and an overbust measure of 36.5 inches. Since 36.5 - 33.5 = 3, Mary's cup size is a C. Since 33.5 gets rounded to 34, her band size is 34. Thus, Mary's bra size is a 34C.

Women with Large Breasts

Women who have larger breasts will often get a better fit if they go with a smaller band size and larger cup size. For example, if you measure your bra size as 38D using the method above, you may find that a 36E bra fits nicely too. Finding a bra that fits well depends not only on the number, but also on your breast shape and style of the bra.

Common Misconception About Band Size

Many women ask, "Aren't we supposed to add 5 inches to the underbust measure to get the band size?" The answer is, "Only if you plan to time travel back to 1950."

In the old method of brassiere sizing, women were told to add 4 to their underbust if it was an even number, and add 5 if it was an odd number. This method was based on the sizing scheme of a particular bra manufacturer many decades ago. Most bras today are not sized according to this scheme. Any bra sizing calculator that tells you to add 5 is using outdated information! Do not add 5.

Exception: Specialty brands of brassieres sometimes have their own methods of measuring and sizing that may be slightly different from the standard method above. If a bra manufacturer has a website, there will be a section that tells you how to measure yourself to calculate the right size. The standard method above works for the brands of bras found in department stores.

Common Misconception About Cup Size

It is commonly believed that a B cup is always smaller than a C cup, a C cup is always smaller than a D cup, etc. In fact, cup size is relative to the band size. Cup size measures how far your breasts stick out, not their volume.

For example, the cup volume of a 38B bra is actually greater than the cup volume of a 34C bra. Some women's breasts are wider and flatter, some women's breasts are narrower but protrude more.

How Accurate Are Bra Sizes?

Your bra size should be used as a guide, not an absolute measure. When trying on bras, women should not overlook bras that have smaller/larger cup sizes, and smaller/larger band sizes. Two bras made by different companies can both labeled as 36B, but one may fit terribly and one may fit perfectly.

© Had2Know 2010