The majority of women are wearing the wrong bra size, and this is especially common among curvy and full-bust women who have been relegated to limited size ranges for too long. This guide changes that.
How to Measure Yourself
Measure your underbust (the circumference directly under your breasts) while wearing a non-padded bra or nothing. This is your band size — round to the nearest even number.
Measure your bust at its fullest point, keeping the tape parallel to the floor.
Subtract your band measurement from your bust measurement. Each inch of difference corresponds to a cup size: 1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD/E, 6 = F, 7 = G, etc.
Sister Sizes Explained
If a 36D is too tight in the band but the cup fits, try a 34DD — same cup volume, smaller band.
If a 36D is too loose in the band but the cup fits, try a 38C — same cup volume, larger band.
This is called sister sizing and it's essential knowledge when shopping across different brands that size differently.
Signs Your Bra Doesn't Fit
Band rides up: the band is too large. The band should be horizontal and firm.
Cups gape or wrinkle: the cup is too large. Cups that overflow or create a 'double boob' effect are too small.
Straps fall off your shoulders: they're too loose, or the bra style doesn't suit your shoulder slope.
Where to Get a Professional Fitting
Specialty lingerie stores (not department stores) offer the best fittings. Bravissimo, Nordstrom, and independent lingerie boutiques are great options.
UK specialty brands (Freya, Elomi, Panache) tend to have more accurate sizing systems. Many curvy women find their 'true' size in UK sizing.
Online communities like r/ABraThatFits on Reddit offer detailed fitting guides and community help.
Understanding the Relationship Between Cup and Band
The most important principle in bra fitting that most women don't learn: cup size is relative to band size, not absolute. A 34D and a 36C contain the same cup volume — the cup letter changes as the band size changes (this is called sister sizing). If your bra fits perfectly in the cup but the band is too loose, going down one band size and up one cup size maintains cup volume while tightening the band. Understanding sister sizes dramatically increases the range of bras you can fit successfully.
The Fitting Room Test
A bra fits correctly when: the band lies horizontally and you can fit two fingers under it without pulling; the underwire (if present) follows the breast root exactly without sitting on breast tissue; the cups contain all breast tissue with no overspill at the top, sides, or bottom; the centre gore lies flat against the sternum — if it floats off the body, the cups are too small; and the straps provide support without digging. A bra that doesn't meet all these criteria in the fitting room will not meet them after purchase.
Where to Get a Professional Fitting
Professional bra fittings for larger cup sizes: specialist lingerie boutiques (not department store bra fitters, who are typically trained on a limited size range) provide the most useful service. Online communities including r/ABraThatFits (which has a comprehensive fitting guide) allow self-fitting with guidance from experienced community members — the online guide and community are often more accurate than in-store fitting from undertrained retail staff. UK readers: Bravissimo and Rigby & Peller offer specialist fittings in extended sizes.
Frequently Asked Questions
How do I know my correct bra size?
Measure your underbust (band size) and your fullest bust point, subtract the band from the bust to find your cup size. Try the bra on and check the four signs of fit: band position, cup fill, strap stability, and underwire placement.
What bra size is considered plus-size?
Bra sizing doesn't have a single 'plus-size' cutoff. Full-bust is generally considered 28–44 in band with a D cup or larger. Many specialist brands serve up to a 50 band and K cup or beyond.
What are the best bra brands for large busts?
Elomi, Panache, Freya, Fantasie, Goddess, and Anita are consistently recommended for full-bust women. All offer excellent construction in extended sizes.