Finding the right bra can be especially difficult if you are just between available sizes or you want a fit that’s a little lighter or tighter than the average. Understanding how to use sister sizes can make it a lot easier by giving you options that provide those benefits, making it a little easier to gain control over your own comfort.

Determining Your Sister Size

A sister size is a different band size with the same space in the cup as your base size. To accurately calculate your sister sizes, you need to know your proper bra size from measurements. That can be determined easily if you use a detailed bra quiz that includes measurement instructions and explanations.

Cup size is relative to band size, since it is determined by your overbust measurement. That means a smaller cup in a bigger band size may have the same volume as the size you measure. By going up or down band sizes and adjusting your cup size proportionally, you can get the fit you want. Those sizes that have the same volume in the cups at different band lengths are sister sizes.

Every two inches of band size changes the cup by one. For example, a person who wears a 38D could also choose a 36E (DD) or 40C to get the same volume. Adjust the cup upwards when going down a band size for a tighter fit, or adjust it downwards when going for a looser fit the next time you shop.

Sister Size Bra Chart

If you have trouble remembering bra sister sizes or you are working with a sizing system that includes half sizes or one-inch band size increments, you might need a chart to help you locate the best options. This does make figuring out your perfect fit a little more complicated, but more precise sizing also means that you can get even closer to the center of your comfort zone when you do the work. It’s also easy to make your own chart with a little time and creativity, allowing you to see all the sisters to your current bra size at once.

Bra Styles and Comfort

Women tend to land on their favorite bra style by finding one that works with their bust type and fit preferences, but there are times when specific styles are dictated by necessity. For example, a good t-shirt bra is going to look better than any other style under a t-shirt. That’s what it is made for. Similarly, there are times when you just need a strapless fit for a specific dress. Sister sizing can make that change easier by allowing you to fine-tune your comfort, so you could wear wireless bras in 36C but prefer a 38B for anything with a wire, for example.

Now that you get the idea, it’s time to check it out in practice. Pick a bra style that is just slightly uncomfortable but still the right size and try on a sister size for that bra to see if it helps you out.