How to Determine Your Bra Size

The cup size is not an absolute, unchanging measurement. This is a common misconception about bra sizes: a D cup looks the same for every band size, or having a smaller bust automatically means you’re an A cup. In reality, the cup size changes proportionally with the band size—meaning it depends on the band size. For example, a 32D will have a smaller volume than a 36D, but both are D cups.

How does a well-fitted bra make you feel and look? There are several signs that indicate whether a bra fits you properly. Here’s what to look for when measuring or trying on different bra sizes:

• The band fits snugly: The band, not the straps, is responsible for supporting your breasts. You should only be able to slide one or two fingers under the band.
• Full coverage on the sides: A well-fitted bra won’t let your breasts spill out on the sides or under the armpits. For underwire bras, check if the wire ends point toward the middle of your armpit—this indicates a good fit.
• The center lies flat: The center gore (the part between the cups) should lie flat against your chest without digging into your skin. If it doesn’t, the bra isn’t the right size.
• Smooth silhouette: Avoid the “double boob” effect caused by cups that are too small, which dig into the breast tissue. A proper fit ensures a smooth, seamless look without any bulging.

Consider different breast shapes. What if you’ve found the right bra size, but it still doesn’t fit well? You might have chosen the wrong style for your breast shape. Here’s how to address common breast shape issues:

• Wide-set breasts: If your breast tissue is spread over a wider area and doesn’t project much, you likely have wide-set breasts. (Another clue: breast tissue near your collarbone, even if your breasts are relatively small). Horizontal cup bras work best for wide-set breasts, with cups that have a straight-across cut. Avoid V-shaped cups.
• Bell-shaped breasts: If your breasts are narrower at the base but fuller at the bottom, don’t worry! Opt for bras with underwire, separated cups, and wider coverage. Avoid horizontal or V-shaped cups.

Understand sister sizes. If you’ve found a bra that’s almost perfect but not quite, try its sister size. Sister sizes are bra sizes that are close enough to compensate for variations between brands.

• Go down a size: Decrease the band size by two units but increase the cup size by one. For example, go from 36C to 34D.
• Go up a size: Increase the band size by two units but decrease the cup size by one. For example, go from 36C to 38B.

Learn about bra sizing systems. There are currently two different bra sizing systems (outlined below). The modern system is more commonly used, but some manufacturers still rely on the traditional system. Unfortunately, it’s hard to know which system a brand uses. Here’s how to minimize the risk:

• If you’re trying bras in-store, know your size in both systems.
• If shopping online, look for websites with flexible return policies.

Be cautious when relying on store fitters. Getting measured by an experienced fitter is great if you’re unsure about your bra size—they can suggest styles that suit you. However, keep these tips in mind to ensure a proper fit:

• Avoid stores with limited size ranges. Staff might push you into buying a bra that’s not quite right but is in stock. Before committing, ensure the store carries smaller band sizes (like 28 and 30) and larger cup sizes (DDD and above). In the U.S., reputable stores like Nordstrom and Dillard’s are good options.
• Ask for sizing in both systems. This way, you’ll know which size to try if one system leads to a poor fit.
• Don’t wear a bra during measurements. If the fitter tries to measure you while you’re wearing a bra, the results may be inaccurate. If you’re uncomfortable, wear a thin, snug tank top and remove your bra for the measurement.

Measure the band size. This is the easiest part of the process—the band size is relatively stable and straightforward to measure.

• Wrap the measuring tape around your torso just below your bust, ensuring it’s level and snug. Keep your arms relaxed at your sides. Record the measurement in centimeters.
• For bras using inches, if the measurement is an odd number, try bras one size smaller or larger. For example, if you measure 31 inches, your band size could be 30 or 32.
• If the measurement is even, a bra with that band size will likely fit, but you might need a smaller or larger size depending on your body shape.

Determine the cup size. Remember, cup size isn’t absolute—it changes proportionally with the band size.

• Bend forward so your chest is parallel to the ground. This position helps measure the entire breast volume, not just the projection when standing upright.
• Wrap the tape around the fullest part of your bust without pulling too tight. Record the measurement.
• Ensure the tape is parallel to the ground and doesn’t slip down your back. Use a mirror or ask a partner or friend to assist for accuracy.
• Calculate the cup size by subtracting the band size from the bust measurement. The difference determines your cup size:
  • Less than 2.5 cm = AA
  • 2.5 cm = A
  • 5 cm = B
  • 7.5 cm = C
  • 10 cm = D
  • 12.5 cm = DD
  • 15 cm = DDD (E in UK sizing)
  • 18 cm = DDDD/F (F in UK sizing)
  • 20.5 cm = G/H (FF in UK sizing)
  • 23 cm = I/J (G in UK sizing)
  • 25.5 cm = J (GG in UK sizing)
  • Most top brands use the UK cup size system: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K, KK, L, LL. In the U.S., you might see sizes like DDD or DDDD, equivalent to E and F. For larger cup sizes, refer to an international bra size chart if unsure.

Try on the bra with the band and cup size determined above. Don’t consider this your exact size until you’ve tried on a few bras, as sizes can vary between brands and styles.

Put on your bra correctly. The “scoop and swoop” method ensures your breasts are fully positioned within the cups:

• After unhooking the bra, extend the shoulder straps. Slip your arms through the straps and lean forward slightly to let your breasts settle into the cups.
• Fasten the bra using the outermost hooks. Don’t worry if it feels tight—this is normal if you’re trying a smaller band size. Stretch the band to hook it securely.
• While still leaning forward, hold the underwire and adjust it to ensure your breasts are comfortably seated in the cups.
• Slide your hand into one cup and gently pull the breast tissue toward the center. Repeat on the other side.
• Adjust the shoulder straps. Slide them off your shoulders and tighten the sliders so they’re snug but not digging into your skin.

Check the band size. The correct band size is the smallest size you can wear comfortably. (It might be smaller than your actual underbust measurement—bra bands are stretchy, especially for sizes 42+). The band should be snug enough to provide support without relying too much on the shoulder straps.

• You should be able to slide a finger under the band but not much more. A general rule is that you can fit a fist under the back of the bra, just above your spine.
• The bra should fit comfortably on the loosest hook but may feel too tight on the tightest hook. This design allows you to tighten the band as the fabric stretches over time.
• If the band feels loose even on the tightest hook, try a smaller band size with a larger cup. For example, if 32D is too loose, try 30DD. Remember to adjust the cup size when changing the band size—each time you go down a band size, go up a cup size to maintain the same volume.
• If the band feels painfully tight, try going up a cup size. A too-large band might seem tight if the cups are too small. If increasing the cup size doesn’t help, try going up a band size and down a cup size, e.g., from 28G to 30FF. However, try the first method before resorting to this.

Check the cup fit. A well-fitted cup fully encases your breasts without wrinkling or gaps. Spillage or “double boob” indicates the cups are too small, even in push-up bras.

• Check around the cups for any breast tissue spilling out, not just at the front but also under the arms.
• Ensure the underwire follows the natural curve of your breasts and lies flat against your ribcage.
• Check under your arms to ensure the underwire sits on your ribs, not on soft breast tissue. If the wire digs into the side of your breast, try a larger cup size. If you’re used to wearing bras with too-large bands and too-small cups, your breast tissue may have migrated, making your breasts appear pushed toward your armpits or back. This issue can resolve once you find the right fit.
• If the center gore presses painfully into your sternum, try a smaller cup size or a plunge bra with a deeper center. This is often a cup issue, not a band issue. Alternatively, your ribcage shape might be the cause. In this case, give yourself time to adjust or opt for bras with a lower center gore.
• If you suspect the cups are too small but aren’t sure, try a larger cup size to confirm. The difference will be clear if the smaller cup feels tighter.

Evaluate the fit with outerwear. Once you’ve found a well-fitting bra, which might differ in size or style from what you’re used to, it’s time to see how it enhances your silhouette! If you’re wearing a t-shirt bra, ensure it creates a smooth line under your clothes.

• When viewed from the side, your bust should sit midway between your elbow and shoulder.
• A properly fitted bra lifts your bust to the right position. Many find their clothes fit better, and they notice a more defined waistline. If your bust previously sagged due to poor support, you might even need a smaller dress size.
• Tight-fitting shirts reveal spillage from cups that are too small, while overly padded bras show visible lines at the cup edges. Choose a bra color that blends with your skin tone or outerwear to avoid visibility under thin or light-colored fabrics.
• Some worry that a snug band creates back bulges. In reality, bulges occur when the band is too loose and rides up. A properly fitted band sits lower and horizontally, preventing bulges.

Measure the band size. Wrap the tape around your ribcage, just below the base of your breasts. Then:

• If the measurement is even: Add 10 centimeters.
• If the measurement is odd: Add 12.5 centimeters.
• Note that most brands no longer use this sizing method. The “add ten” approach was used by Warners in the 1930s when bra design was in its infancy and doesn’t align with modern bras. However, it’s good to know this system exists.

Measure the cup size. Stand straight and wrap the tape around the fullest part of your bust. (Keep the tape as level as possible—ensure it doesn’t sag at the back.) Subtract the band size from this measurement to determine the cup size:

• Less than 2.5 cm = AA
• 2.5 cm = A
• 5 cm = B
• 7.5 cm = C
• 10 cm = D
• 12.5 cm = DD
• 15 cm = DDD (E in UK sizing)
• 18 cm = DDD/F (F in UK sizing)
• 20.5 cm = G/H (FF in UK sizing)
• 23 cm = I/J (G in UK sizing)
• 25.5 cm = J (GG in UK sizing)

• Avoid buying poorly fitting or low-quality bras just because they’re cheap. When it comes to bras, you get what you pay for. It’s better to invest in one well-fitting bra than to buy three uncomfortable ones!
• To extend the lifespan of your bras and prevent stretching, never wear the same bra two days in a row, even if it’s been washed. Aim to have at least three bras to rotate, allowing the fabric to fully recover its elasticity before being worn again.
• Don’t assume you’ll wear the same size in every bra style or that you can buy any bra in your “true size” without trying it on. Different bra styles suit different breast shapes, so two people who wear the same size in one style might need different sizes in another.
• A well-fitted bra provides 90% of its support from the band, with only 10% coming from the shoulder straps.
• If your breasts are uneven, choose a bra that fits the larger side. You can adjust the strap on the smaller side for extra support. For significant size differences, consider using a silicone bra insert on the smaller side.
• Ignore anyone who insists on determining your bra size solely based on body measurements—especially if they suggest adding extra centimeters to your underbust measurement. Like dress sizes, bra sizing has evolved, and outdated methods no longer apply to modern bras.
• These guidelines are just a starting point—actual fit matters more than measurements. It’s common for two people with the same measurements to wear very different bra sizes due to variations in body shape.
• Those with a D+ cup should opt for bras with multi-panel cups. Side support panels can help narrow the bust, creating a slimmer silhouette.
• Many bra companies act as though women with underbust measurements below 28 don’t exist. However, people do wear sizes like 20, 22, 24, and 26—or even smaller. Remember that bra materials stretch, but unfortunately, brands often ignore smaller band sizes, making them hard to find. Altering bras is an option, but it’s not ideal since underwires can’t be adjusted and may cause discomfort. If you must alter a bra, choose one with a larger band and smaller cup size. Larger bands have longer underwires, so a smaller cup ensures a better fit. For cups larger than D, sizing varies significantly between brands, so consult reviews or ask for recommendations before buying online.

• Soft measuring tape
• Bras to try on