Sizing for my handmade clothing and for my patterns relies primarily on actual body measurements. I prefer to work with actual measurements because sizing conventions vary so much from brand to brand and country to country, and using specific measures eliminates some of the confusion that comes from vanity sizing and gradual industry shifts over time.
I work primarily with imperial units and inches. For metric measurements, there are many calculators to convert between the two systems such as this one, and I’m always glad to help.)
HOW TO MEASURE
For best results, it’s ideal to have someone help you to carefully take your measurements and then use those to choose your clothing and pattern sizes. Four measurements are key for most intimate wear: the full bust measurement, the underbust measurement, the waist measurement, and the full hip measurement. For clothing, measure over the same kind of foundational garments or underwear that you would wear under the garment. For lingerie, measure over a non-padded, thin bra that fits well.
Bra sizing can be a particular tricky puzzle, as many women know all too well. The simplest way to measure bra sizing is to find the difference between the full bust measurement and the underbust measurement. (Full bust – underbust = inches of difference). Each inch of difference represents a cup size, such that 1 inch is an A cup, 2 inches is a B cup, 3 inches is a C cup, and upwards.
This simple method can work well for some women and for fitting simpler bra styles like bandeaus, bralettes, or bras made from materials incorporating stretch which can conform more easily to the many shapes and tissue distributions of the human body. For underwired bras and fabrics with less give, as well as for larger sizes which require more support, accurately measuring and assessing size and shape is a more complicated but very worthwhile process. (More on this subject here.)
To choose your pattern size, begin with your high bust measurement. I use this raw measurement to label my pattern sizes, so there’s no confusion in translating what a size actually means in terms of body measurements or compared to other brands. If your high bust measurement is 36, choose the pattern size 36. If the pattern includes sizes for different cup sizes, each size will be labeled with the cup size as well, though it’s important to note that this doesn’t necessarily mean you should choose the same size as your bra size. If you wear a standard US 36B bra size, your upper bust may not actually measure 36″. Always go with the actual body measurement.
The high bust measure is taken higher than the full bust, above the fullness of breast tissue. The idea is to find the pattern that best accommodates the bone structure of the chest, which tends to best fit the neck and shoulders that the garment hangs from. Areas like the waistline and hip line, while still important for fit, can be adjusted with less difficulty than the upper body where the fit and angles of the neck, shoulders, and chest all affect one other.