The thing about sister sizing is… every bra maker and their mother has written about it. Amy of Cloth Habit, The Lingerie Addict and even Victoria Secret have had a word or two on the subject. Well, I’m joining the (cool) club and chiming in, mostly how you can use it to find your sister size if you don’t exactly fit into a particular band/cup size on the Madalynne X Simplicity 8229.
What is Sister Sizing?
One of my favorite bra making aphorisms is “fuzzy side up, picot edges inside.” It was even worthy of an Instagram post. Well, here’s one for sister sizing, “B is not a B is not a B.” You can thank Amy for that one. Another: “Cups are relative to band.” That came from Amber.
Sister size refers to different bra sizes that have the same cup volume even though the band size and cup letter are different. An example is a 34A and a 32B – they have the same cup volume, but a different band size. As the band size gets larger, cups will have the same volume only if the letter gets smaller. An easy way to think of it is that their reciprocals. As one moves up, the other moves down and vice versa.
Sister Size Down
This means one size smaller for the band and one letter bigger for the cups. Example: if you wear a 34C, your sister size down would be 32D.
Sister Size Up
This means one size larger for the band and one letter smaller for the cups. Using the same example as above, if you wear a 34C, your sister size up would be 36B.
How to Use Sister Sizing
The chart below represents all the sizes that are available for the 8229. If you can’t find your size on the chart, there may be a chance that there is a sister size you can use. One example that I used this past weekend during a 1-on-1 session using a 42DD pattern for a woman that measured a 44F.
If You Use Your Sister Size, Do You Need To Make Changes To The Pattern?
Yes. The cup volume is the same, but the band size is different. When you take your sister size, you’ll have to increase or decrease the band, but this is a very easy adjustment. Amy demonstrates it here.
Sister Sizing Isn’t Always Correct:
You can’t always use your sister size. As Amber demonstrates in her post, sister size patterns aren’t always the same. In her post, she compares two sister sizes and explains that cups/frame can have different slopes/angles to allow for a shift in the distribution in weight while maintaining the same cup volume. Well said, Amber! Looking at the Simplicity 8229, the cup and frame patterns for the 34A and the 32B are not exactly the same. The 34 is slightly taller. I think that is okay because the difference is so small.
I also don’t suggest going up or down more than two sister sizes. As Amber and I show, the differences can get bigger the more sizes you jump.
Last, I HAVE read that sister sizing is a way for retailers to sell limited inventory instead of a bra that actually fits. Not sure if I believe that, but thought I’d mention.
Lace fabric in intro image is from Lacetime