Determining your correct bra cup size is important for getting a bra that fits comfortably and provides proper support. There are a few simple steps you can take at home to measure yourself and figure out your cup size.
What do bra cup sizes mean?
Bra cup sizes are based on the difference between your bust measurement and your band size (underbust measurement). Cup sizes are labeled using letters, with A cup being the smallest and increasing from there.
Here are some key things to know about cup sizes:
- A = 1 inch difference between bust and band size
- B = 2 inch difference
- C = 3 inch difference
- D = 4 inch difference
- DD or E = 5 inch difference
- DDD or F = 6 inch difference
- G, H, etc. continue with 1 inch increases
So if your underbust is 32 inches and your bust size is 36 inches, your cup size would be a D, since there is a 4 inch difference between those two measurements.
How to measure your bra size
To determine your correct bra size, you’ll need to take two key measurements:
- Underbust measurement
- Bust measurement
It’s best to take these measurements without a bra on. Here are step-by-step instructions for each measurement:
Underbust measurement
- Wrap a tape measure around your torso right under your bust. Make sure the tape is level and fits snugly without digging into your skin.
- Exhale and measure to the nearest whole inch. This is your band size.
- If the measurement falls between two whole numbers, round up to the next even number. For example, 31.5 inches would round up to 32 inches.
Bust measurement
- Wrap the measuring tape around the fullest part of your bust. Make sure the tape is level.
- Keep the tape comfortably tight without squeezing breast tissue.
- Measure to the nearest whole inch while standing with your arms at your sides and breasts unsupported.
Take the bust measurement a couple times to make sure you have an accurate number. Remember to breathe normally and not to intentionally expand or contract your chest.
Calculate your cup size
Once you have your underbust and bust measurements, you can use their difference to determine your cup size:
- Subtract your band size from your bust measurement.
- The difference in inches determines your cup size based on the chart below.
| Difference in inches | Cup size |
|---|---|
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | D |
| 5 | DD/E |
| 6 | DDD/F |
For example:
- Underbust: 32 inches
- Bust: 36 inches
- 36 – 32 = 4 inch difference
- 4 inches = D cup
So if your underbust measurement is 32 inches and your bust is 36 inches, your bra size would be 32D.
Tips for accurate measuring
To get the most accurate measurements for determining your bra size, keep these tips in mind:
- Measure braless – take measurements without a bra on for the most accuracy.
- Stand up straight – stand with your arms at your sides and shoulders back to measure properly.
- Breathe normally – don’t intentionally expand or contract your chest while measuring.
- Tape measure should be snug – keep the measuring tape fitted close without compressing breast tissue.
- Measure several times – measure at least twice to ensure you have the proper bust measurement.
- Round up band size – if the underbust measurement falls between inches, round up to the next even number.
Common measuring mistakes
Avoid these common measuring errors that can result in the wrong bra size:
- Measuring over clothes or bra
- Measuring with arms overhead – this expands the bust
- Breathing in and expanding chest when measuring
- Having the tape measure too loose or too tight
- Not measuring parallel to the floor
- Not rounding band size up to the next even number
How cup size changes during certain times
It’s normal for your bra cup size to fluctuate somewhat throughout the month and at certain times:
During your menstrual cycle
Hormone changes during your menstrual cycle can cause your breasts to swell and feel tender or fuller before your period starts. This fullness and swelling may temporarily increase your cup size during parts of your cycle.
During pregnancy and breastfeeding
When pregnant or breastfeeding, it’s common for your cup size to increase significantly as your breasts grow and change shape. Make sure to get fitted regularly throughout pregnancy and breastfeeding.
Weight changes
Gaining or losing a significant amount of weight can affect your breast size and therefore your bra cup size. If your weight changes by 10 pounds or more, get refitted for a bra.
With aging
Breast tissue tends to lose elasticity and fullness with aging. Your cup size may decrease slightly over time after menopause. It’s a good idea to get refitted every year or two as you age.
How to determine cup size without measuring
If you don’t have a measuring tape available, you can still estimate your cup size:
Look at your current bra’s label
Check what cup size you currently wear in your favorite, best-fitting bra. This gives you a starting point or range for trial and error.
Try bras on in sister sizes
Sister sizes have the same cup volume but a different band size. Trying on a range of sister sizes can help you hone in on the best cup fit.
For example, if you think you might wear a 34D:
- Try on 32DD (same cup volume, smaller band)
- Try on 36C (same volume, larger band)
Do a visual and feel check
Look at how your breasts fit into a bra and feel whether it seems like the right cup volume. Signs the cup size is too small include bulge, overflow, and quadding. Gaping cups often indicate the cup size is too big.
Enlist help getting fitted
Make an appointment to get professionally fitted at a bra shop or lingerie store. An experienced fitter will be able to assess your breast shape and tissue distribution and bring you many bra size options to try on.
Other factors that affect bra fit
Cup size is just one component of finding a bra that fits well. You also need to consider:
Band size
The band should fit very snugly without bulging, riding up, or feeling uncomfortable. Make sure to hook it on the loosest setting when trying on.
Cup shape
Bras come in different cup shapes. The best one for you depends on your breast shape and whether they are more shallow vs projected.
Wire width
Wires that are too narrow or wide can make cups fit uncomfortably. Pay attention to whether the wires fully encase your breast tissue.
Breast shape
Breast shape factors like width, fullness on top or bottom, and spacing between can affect what bra styles fit you best.
Breast placement
Wearing the wrong bra size for breasts that are wide-set, close-set, or have asymmetry may cause gaping, overflow, or poking in cups.
How to measure other bra dimensions
In addition to band size and cup size, some other bra measurements can be useful for finding good fit:
Strap length
To measure strap length:
- Fasten the bra straps as if you were wearing the bra properly.
- Using a ruler or measuring tape, measure from where the top of the bra cup meets the strap down to the fastening point of the strap on the band.
The right strap length will keep the bra cups firmly in place without digging painfully into your shoulders.
Underbust full coverage
To measure underbust full coverage:
- Wrap a measuring tape around your torso under the bust, under the armpits, across the widest part of your back.
- Exhale and measure to the nearest whole inch.
This measurement can give you an idea of coverage for full coverage bra styles.
Center front height
To measure center front height:
- Put on your best-fitting bra and stand up straight.
- Using a ruler, measure from the top center of the bra cup down to just under your bust.
This helps determine whether a bra’s center gore height will tack and fit properly between your breasts.
Cup width and depth
To measure cup width and depth:
- Lay the bra cup flat and measure across the top of the cup from wire to wire.
- Measure vertically from the top of the cup down to the wire.
These measurements can help assess if a bra cup shape and dimensions will fit your breast shape and size.
How to figure out sister sizes
Sister sizes have the same cup volume but different band and cup measurements. Knowing your sister sizes gives you more options to find an ideal fit.
To go up a sister size, go up a band size and down a cup size. To go down, go down a band size and up a cup size.
For example, if you normally wear 34DD:
- One sister size up is 36D
- One sister size down is 32E
- Two sister sizes up is 38C
Trying both larger and smaller sister sizes can help you hone in on the perfect fit if you fall between standard bra sizes.
Signs of a good bra fit
Here are signs that a bra fits properly and is the right cup size for you:
- Breasts are fully encased in cups, no bulging over top or sides
- Underwire follows the natural curve under breasts
- Can comfortably fit just two fingers under the band
- Straps stay in place on shoulders without digging in
- Bra feels secure and supportive when moving
- No gaping space at the top of the cup
- Breasts centered in cups without overflow or empty space
What if you need two different cup sizes?
It’s not uncommon for women to require two different cup sizes, like two different shoe sizes. Breast asymmetry is normal.
If one breast is significantly larger than the other, you may get the best fit by:
- Trying bras specifically designed for asymmetry
- Wearing a padded insert or cookie in the smaller cup
- Going up a cup size to fit the larger breast and then having the smaller cup taken in
Don’t just settle for an average size if one breast has a very different fit need. Work with an expert fitter to accommodate asymmetry.
When to get refitted for a bra
You should get refitted and possibly sized for new bras about once a year. Also get refitted if:
- You’ve gained or lost weight
- You’ve gone through a major life change like pregnancy
- Your bras start feeling uncomfortable or ill-fitting
- The bra straps fall down constantly
- Your breasts seem to overspill or not fill out the cups
- You have quad boob, gapping, poking, shoulder indentations, or red marks
Even if your weight has stayed the same, bra size can change over time. Make regular professional bra fittings part of your self-care routine.
Conclusion
Figuring out your correct bra cup and band size is simply a matter of taking accurate bust and underbust measurements. Make sure to measure braless, breathe normally, and not compress breast tissue. Use the difference between the two measurements to calculate your cup size. Remember that things like menstrual cycles, pregnancy, and weight loss or gain can affect cup size. Stay on top of regular bra fittings to maintain optimal fit and support as your body changes.