Size Calculator

Knowing your proper bra size is the first step in finding the most comfortable bra for you.
Use our calculator to get your size and let us do the work for you.

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 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.


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.

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.

An overview of 2 main methods used on the market:

1. The "Plus 0"

Using the “plus 0” method, your underband measurement IS your underband size. If you measure 34’’, you wear a 34 band.

This method gives you a firm and supportive fit. If you prioritize support, lift, and shoulder/back relief and don’t mind a tight band around your ribcage, this method is the right one for you. This sizing method is popular among brands that offer fuller bust bras (DD+ cups).

2. The "plus 4"

Using the “plus 4” method, your underband measurement plus 4 ish (rounding up or down if it’s an odd number) is your band size. If you measure 34’’, you wear a 38 band. This method gives you a relaxed and unsupportive fit. If you prioritize coverage and ribcage comfort over support and lift, this method could work for you. This sizing method is popular among brands that only carry up to DD cups.

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.

Our calculator doesn’t use “plus 0” or “plus 4.”

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 take your preference into account. We ask that you measure your underband as tightly as you'd like your bra to fit, then add 2'' to get the band size.

If you prefer a firm and supportive fit, you will get a smaller band size (and bigger cup size). If you prefer a loose
and relaxed fit, you will get a bigger band size (and smaller cup size).

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