Finding a bra that fits starts with measuring your underbust and fullest bust, then using the difference to determine your band and cup size.
For the full breakdown, see our best Compression Bra After Breast Augmentation Surgery guide.
One wrong measurement lands you in a band that rides up or cups that gape. The fix takes two minutes, a soft tape measure, and one rule: the band does 80–90% of the work. Here’s the exact sequence that eliminates the guesswork.
Measure Band Size Correctly
Band size is the foundation, so get this right first. Wear a non-padded bra or go bare. Wrap the tape snugly around your rib cage, right under your bust, keeping it parallel to the floor. Exhale fully (the smallest measurement is the one you want) and let two fingers slide under the tape — snug, not tight. Round to the nearest whole number: that’s your band size using the modern standard. The older “add 4 inches” method often overestimates band size and should be skipped.
Measure Bust Size and Calculate Cup
Wrap the tape around the fullest part of your bust — typically across the nipples — without compressing any breast tissue. Keep the tape parallel to the floor and flat against the skin. Round to the nearest whole inch: if the measurement lands on a half-inch, round up. Now subtract your band number from your bust measurement. Each inch of difference equals one cup letter: 1 inch is A, 2 is B, 3 is C, 4 is D, 5 is DD or E, and so on. Combine the band number and cup letter for your starting size — something like 36D.
The Fit Verification (Do This Before Buying)
Numbers alone don’t guarantee a good fit.
- Band fit. The band should sit level around your torso and not ride up. Pull it away from your back — if more than two inches gapes, try the next smaller band size.
- The scoop and swoop. Reach under the band from the side, scoop all breast tissue upward, and tuck it fully into the cup. If tissue bulges at the top or sides, the cup is too small. If the fabric gapes, it’s too large.
- The gore. The center piece between cups should lie flat against your breastbone. If it floats away, you likely need a larger cup.
- Underwire track. The wire should follow your breast’s natural crease and never rest on breast tissue. For wireless bras, check that the bottom seam follows the same line.
- Straps. Snug enough to stay up without digging in. If one side needs a different adjustment than the other, that’s normal — bodies are asymmetrical.
Common Fit Mistakes (And What to Do Instead)
Most bra fit problems come from a loose band — the straps get tightened to compensate, but that shifts all the tension to your shoulders. The band is the load-bearer, not the straps. When the band fits right and the cups hold all tissue without overflow or gaps, you’ve found your size. If the fit between two sizes feels almost right, sister sizing can nudge it: same cup volume but a different band and letter combination (for instance, 36D and 38C hold the same breast volume).
FAQs
Should I measure while wearing a padded bra?
No. Padding distorts the bust measurement. Use a non-padded bra or no bra to get an accurate reading of your natural breast volume.
What if my measurements give me a size that doesn’t match any brand’s chart?
Brand sizing varies — always check the specific brand’s size chart before ordering. The two-measure method gives a starting point, not a universal guarantee.
How often should I remeasure?
Every six months or after significant weight changes, pregnancy, or nursing. Rib cage and breast tissue can shift over time without your clothes feeling any different.
References & Sources
- Breast Cancer Now. “Your guide to a well-fitting bra.” Step-by-step fit checklist and band support principles.
- National Breast Cancer Foundation. “Bra Fit Guide.” Measurement instructions and sister-size chart.
- The New York Times Wirecutter. “How to Find a Bra That Fits.” Research-based testing and common fit mistake breakdown.