Size Calculator

The size calculator is intended as a starting point.
If you've tried different sizes and know the one that works for you, choose the size you normally wear.
Not convinced? Book a virtual fitting with our team.

Step 1
Let's Measure Your Underband
Wrap the measuring tape around your ribcage, directly under your bust, as tightly as you'd like your bra to fit.
Step 2
Now Your Leaning Bust Measurement

Lean forward about 45 degrees and loosely wrap the measuring tape around the fullest part of your bust. For most accurate results, measure without a bra.

Now Your Standing Bust Measurement

Loosely wrap the measuring tape around the fullest part of your bust. For most accurate results, measure without a bra.

Step 4
Fit Preference

With relaxed fit, expect less lift and a more forgiving band. Best for people who don't want to alter the natural shape of their breasts and prioritize ribcage comfort. We use the +2 method to calculate your size.

With firm fit, expect more support and a tighter band. Best for people looking for major lift and don't mind a tighter band around the ribcage. We use +0 to calculate your size.

For more information, read our FAQ below.


Our calculator uses "plus 0" and "plus 2", depending on your preference for a firm or relaxed fit.

If you prefer a firm and supportive fit, prioritizing shoulder relief and separation, you will get your "plus 0" size. It will be a smaller band size, and a larger cup size.

If you prefer a loose and relaxed fit, prioritizing ribcage comfort and keeping the natural breast shape, you will get your "plus 2" size. It will be a larger band size, and a smaller cup size.

Our size calculator measures your underband differently. Loose underband and tight underband can differ by 4’’ or more. Instead of taking an average of the two, we ask that you measure your underband as tightly as you'd like your bra to fit. If you are familiar with size calculators that take loose, snug, and tight measurements, our measurement will be closest to "snug."

Measure tighter if: your bra band tends to ride up in the back and gets pushed down in front (the “seesaw effect”), the straps are too far apart and cut into your armpit, or you prefer a firm fit.

Measure looser if: you have ribcage sensitivities, you have a more muscular body type, you only want nipple coverage with minimal support, or you prefer a relaxed fit.

We recommend checking the following for the right fit:

1. The bra band should stay put without being uncomfortably tight. It should be parallel to the floor, not riding up in the back.
2. Shoulder straps shouldn’t dig in, slip off, or cut into your armpits.
3. Your breasts should be contained in the cups without overflow or gaps.
4. The underwire should contour your breasts without poking anywhere.
5. Generally, the center gore should lie flat against your chest. However, if your breasts are touching when supported (there is no room for the center gore between your breasts), you are wearing a wireless bra with no center gore, or you have an inverted sternum, the center gore doesn’t need to lie flat against your chest.

Remember to do the "scoop and swoop" (reaching into the bra cups and scooping all the breast tissue into them). Do this every time you put a bra on.

If you’ve done the trial and error and figured out the size that works for you, choose that size over our calculator. Our calculator is intended as a starting point. It gives you a “middle of the road” size, between super firm and super relaxed, taking into account individual preference as much as possible.

If you suspect your current bra size isn’t right, or you haven’t worn a bra for some time, give our calculator a try.

Understance uses US sizing. If you are more familiar with UK
sizing, here’s a side-by-side comparison of cup sizes: