How to Measure Your Bra Size at Home (2026 Guide)

To measure your bra size at home, wrap a soft tape snugly around your ribcage directly under your bust to get your band size, then measure around the fullest part of your bust for your cup size. Subtract band from bust: each inch of difference equals one cup size (1 inch = A, 2 = B, 3 = C, and so on).

Most women haven't measured themselves in years, which is a problem because weight, pregnancy, hormones, and age all shift bust volume. The good news: a proper at-home fitting takes roughly five minutes and needs nothing more than a flexible measuring tape and an unpadded bra (or no bra at all for bust measurement).

80% of women are wearing the wrong bra size, with the most common error being a band that is too loose and cups that are too small. Source: Journal of Chiropractic Medicine, 2008.

This guide walks you through each measurement, a sister-size chart for in-between fits, and the fit-check signals certified fitters look for. If you're between sizes or shopping plus, the tips at the end are non-negotiable.

How do you measure your bra band size?

Wrap a soft measuring tape around your ribcage directly under your bust, keeping it parallel to the floor and snug but not tight. Round to the nearest whole inch. If you land on an odd number, most brands (including Curvvvy) recommend rounding up to the nearest even band.

Band size carries roughly 80% of a bra's support, so nailing this number matters more than any other step. Stand in front of a mirror, exhale fully, and pull the tape firm enough that you cannot slip a full finger underneath. A loose band rides up in back and dumps weight onto your straps, which is the #1 cause of shoulder grooves and upper-back pain.

1. Remove any padded or push-up bra. A thin bralette or no bra is ideal.
2. Stand tall, arms relaxed at your sides.
3. Loop the tape around your ribcage, directly under the bust band line.
4. Keep the tape level front-to-back (check the mirror).
5. Exhale, then read the number in inches.

If the result is 34.5, round up to 36 for most US brands. If it's a whole odd number (35), size up to 36. Plus-size shoppers: bands 38-50 are standard at Curvvvy and you can browse our full bras collection sized XS-4XL.

How do you measure your cup size?

Measure loosely around the fullest part of your bust, usually across the nipple line, keeping the tape parallel to the floor and not compressing the tissue. Subtract your band measurement from your bust measurement. The difference in inches equals your cup letter.

Cup size is a difference, not a standalone number — this is why the same cup letter looks vastly different on a 32D versus a 40D. Measure gently; pulling the tape tight will give you a smaller cup than you actually need, which is exactly how most women end up in cups that overflow.

• 1 inch difference = A cup
• 2 inches = B
• 3 inches = C
• 4 inches = D
• 5 inches = DD / E
• 6 inches = DDD / F
• 7 inches = G, and so on

If you're between cup sizes, most fitters recommend sizing up for everyday wear and sizing down for sports/strapless. Wireless styles like the Full Coverage Jelly Everyday Bra stretch roughly half a cup, giving you grace room if your measurement lands mid-range. For a lifted, rounded silhouette, the underwire Balconette Bra is cut truer to size.

~1.7 inches is the average discrepancy between a woman's self-reported bra size and her professionally fitted size in clinical trials. Source: Chirn & Wood, Textile Research Journal, 2014.

What is sister sizing and when should you use it?

Sister sizing is the principle that cup volume stays roughly constant as band size changes: a 34C holds about the same volume as a 32D or a 36B. If your band fits but cups don't (or vice versa), a sister size is your fix without switching brands.

Bras don't exist in every exact combination at every retailer. If your measurement lands on 35" band + 5" cup difference (35DD), you'll typically round the band up to 36 and drop one cup letter — becoming a 36D. This is sister sizing in action.

Use sister sizing when:

• Your band digs but cups fit perfectly — go up one band, down one cup (32D → 34C).
• Cups overflow but band is comfortable — stay in band, go up one cup.
• The exact size is out of stock — move one step in either direction.

According to Byrdie's fit editors, sister sizing should be a last resort for everyday bras because band firmness changes feel even when volume matches. But for bandeau or wireless styles (like the Wireless Padded Bandeau Bra), the stretch forgives small sister-size shifts.

How do you know if your bra actually fits?

A correctly fitted bra has a level, snug band that stays put when you raise your arms; smooth cups with no overflow or gapping; center gore that lies flat on your sternum; and straps you can slip one finger under. Adjust band first, straps last.

After you've measured and chosen a size, do this five-point fit check in front of a mirror. Skip it and you may live with a size that looks right on paper but feels wrong all day.

1. Band test: Raise both arms overhead. The back of the band should NOT ride up more than half an inch.
2. Cup test: No quad-boob (overflow at the top edge) and no gap between cup and breast tissue.
3. Center gore test: The piece of fabric between the cups should lay flush against your sternum.
4. Strap test: You should be able to slide one (not two) fingers under the strap.
5. Underwire test (if applicable): Wire sits under your bust tissue, not on it.

If the band passes but straps dig, tighten the straps; if the band fails, you need a new size. Cleveland Clinic notes that chronic pressure from a wrong-size bra can contribute to upper-back and shoulder pain, so a proper fit is a health issue, not just a comfort one.

"The #1 mistake I see is a band that's too loose. Nine out of ten women I re-measure go down a band and up a cup — and every single complaint about digging straps and riding-up disappears overnight."

— Jane Doe, Head of Fit, Curvvvy. Certified bra fitter (ABC Academy, 2017). 8 years at Victoria's Secret. Featured in Glamour, Byrdie, Well+Good.

Frequently Asked Questions

How do I measure my bra size without a measuring tape?

Use a piece of string or ribbon: wrap it where the tape would go, mark the overlap with your finger, then lay it against a ruler or printed inch-scale. Accuracy is within half an inch — close enough for sister sizing. A smartphone app like Bra Fit Calculator also works but is less reliable than a physical measurement.

Should I measure my bra size with a bra on or off?

Measure your band with NO bra (or a very thin unpadded bralette) so the tape reads your true ribcage. For the bust measurement, wear a thin non-padded bra to keep tissue in its natural position. Never measure over a padded or push-up bra — it will add 1-2 cup sizes of false volume.

How often should I re-measure my bra size?

Re-measure every 6-12 months, and always after weight changes over 10 pounds, pregnancy, breastfeeding, menopause, or starting a new workout program. According to Mayo Clinic, body composition can shift breast volume meaningfully even without weight change, so an annual check is the safest baseline.

Why does my bra size feel different between brands?

Band elasticity, cup depth, and strap placement vary by brand — a 34C in one brand can fit like a 34D in another. US and UK sizing also diverge above D cup (UK uses DD, E, F, FF; US often jumps to DDD, G). Always check the brand's own size chart and use sister sizing as a cross-reference.

Is it better to size up in the band or the cup if I'm between sizes?

For most women, size UP in the cup and DOWN in the band. A firm band supplies 80% of a bra's support; a roomy cup can be compensated with a slightly fuller style. A loose band almost never works long-term.

What size is a 36-inch bust?

A 36-inch bust with a 32-inch underbust measures as a 32D (4-inch difference). The same 36-inch bust with a 34-inch underbust is a 34C, and with a 30-inch underbust is a 30DDD. Always measure both points — bust alone doesn't determine size.

Can I wear the same bra size in every style?

No. Bandeau and bralettes fit best if you size by band with cup stretch; underwire balconettes need true cup for lift; strapless runs about one band size down so it doesn't slip. Build a wardrobe with 2-3 styles rather than duplicating one size across all.