Finding the right bra size starts with two simple measurements: your underbust and bust. A bra size combines a band measurement (the number) with a cup size (the letter), such as 34B or 36C.
Use the chart below as a starting point, then check how the bra actually fits—because sizing can vary between brands and styles.
Bra Size Measurement Chart
| Band Size | Underbust Measurement | Typical Bust Measurement for A Cup | B Cup | C Cup | D Cup | DD/E Cup |
|---|---|---|---|---|---|---|
| 30 | 25–27 in | 31 in | 32 in | 33 in | 34 in | 35 in |
| 32 | 27–29 in | 33 in | 34 in | 35 in | 36 in | 37 in |
| 34 | 29–31 in | 35 in | 36 in | 37 in | 38 in | 39 in |
| 36 | 31–33 in | 37 in | 38 in | 39 in | 40 in | 41 in |
| 38 | 33–35 in | 39 in | 40 in | 41 in | 42 in | 43 in |
| 40 | 35–37 in | 41 in | 42 in | 43 in | 44 in | 45 in |
| 42 | 37–39 in | 43 in | 44 in | 45 in | 46 in | 47 in |
| 44 | 39–41 in | 45 in | 46 in | 47 in | 48 in | 49 in |
Important: This is a general reference chart, not a universal sizing standard. Different manufacturers use different sizing systems, and cup volume also changes with band size.
How do I measure my bra size at home?
You need a soft measuring tape and, ideally, an unpadded bra or no bra.
Step 1: Measure your underbust
Wrap the measuring tape directly underneath your breasts, where the bra band normally sits.
Keep the tape:
- Snug but not painfully tight
- Level around your entire torso
- Parallel to the floor
- Flat against your skin
Record the measurement in inches.
Step 2: Measure your bust
Wrap the tape around the fullest part of your breasts. Keep the tape level without pulling it tightly against your body.
Record this measurement in inches.
Step 3: Determine your band size
Your underbust measurement helps determine the band size. Depending on the sizing system and brand, you may need to round the measurement or select the nearest available band size.
For example, an underbust measurement around 31 inches commonly points toward a 32 band, although the manufacturer’s chart should be used for the final selection.
Step 4: Calculate your cup size
A traditional method is to subtract the band measurement from the bust measurement.
For example:
Bust: 38 inches
Band: 34 inches
Difference: 4 inches
A difference of approximately 4 inches is commonly associated with a D cup in traditional U.S. sizing, giving an estimated size of 34D.
However, cup letters are not absolute measurements. A 34D does not have the same cup volume as a 38D.
What is the difference between band size and cup size?
The band size is the number in a bra size and represents the approximate circumference around your rib cage.
The cup size is the letter and describes the difference between the bust measurement and the band measurement.
For example, in 36C:
- 36Â = band size
- CÂ = cup size
A common mistake is thinking that a C cup has one fixed breast volume. It doesn’t. Cup volume changes as band size changes.
How do I know if my bra size is correct?
A properly fitting bra should feel supportive without digging painfully into your skin.
Check these areas:
- Band:Â It should sit level around your back and feel secure on the loosest hook when the bra is new.
- Cups:Â Breast tissue should fit inside the cups without spilling over or leaving significant gaps.
- Center gore:Â For many underwire styles, the center section should sit comfortably against your chest.
- Straps:Â They should stay in place without carrying most of the breast weight.
- Underwire:Â It should surround the breast tissue rather than sitting directly on it.
If the band rides up your back, it may be too loose. If the cups overflow, you may need a larger cup size—or a different bra shape.
What if my measurements put me between two bra sizes?
Try your calculated size plus a nearby size. Bra fit isn’t determined by measurements alone.
For example, if 34C feels too tight in the band but the cup fits, you might try a 36B. These are called sister sizes because they have similar cup volume while using different band sizes.
Common sister-size relationships include:
- 32C ↔ 34B ↔ 36A
- 34C ↔ 36B ↔ 38A
- 34D ↔ 36C ↔ 38B
- 36D ↔ 38C ↔ 40B
The fit won’t be identical because the band circumference and cup dimensions change, but sister sizes can be useful when your calculated size doesn’t feel right.
Does bra size change over time?
Yes. Your bra size can change with changes in body weight, hormones, pregnancy, breastfeeding, aging, exercise, or other body changes.
It’s a good idea to remeasure when:
- Your current bras suddenly feel uncomfortable
- The band starts riding up
- Your cups gape or overflow
- You notice a significant change in your body measurements
- You’re buying a new brand or style
Can I use a bra size chart for every brand?
Not necessarily. Bra sizing is not completely standardized. A 34C from one brand may fit differently from a 34C from another.
When shopping, use your measurements as a starting point and compare them with the individual brand’s size chart. Bra construction, fabric, cup shape, and stretch can all affect the final fit.
What is the easiest way to calculate my bra size?
Measure your underbust and fullest bust, then use the brand’s size chart to convert those measurements into a band and cup size.
For a quick estimate:
Bra size = band size + cup size
Your measurements are a starting point—not a guarantee that one particular size will fit perfectly.
Bra Size Measurement Chart: Quick Reference
| What to measure | How to measure |
|---|---|
| Underbust | Around your rib cage directly beneath your breasts |
| Bust | Around the fullest part of your breasts |
| Band size | Determine from your underbust measurement |
| Cup size | Compare bust and band measurements |
| Final size | Check the specific brand’s sizing chart and fit |
Frequently Asked Questions
How do I measure my bra size without a measuring tape?
You can use a piece of string or ribbon to measure around your underbust and bust, then measure the string against a ruler or other straight measuring tool.
Should I measure my bra size with a bra on?
For the most consistent result, use no bra or a thin, unpadded bra. Padded or push-up bras can change the bust measurement.
Is a 36C bigger than a 34C?
Generally, yes. A 36C has a larger overall cup volume than a 34C, even though both have a C cup.
Why does my bra band fit but the cups don’t?
Your cup size may be too small or too large, or the bra’s cup shape may not suit your breast shape. Try adjusting the cup size while keeping the band size the same.
Why does my bra ride up in the back?
A band that rides upward commonly indicates that the band is too loose. Try a smaller band size while adjusting the cup size as needed.
How often should I measure my bra size?
There is no fixed schedule. Remeasure whenever your bras stop fitting comfortably or your body measurements have changed.
The Bottom Line
The best way to find your bra size is to measure your underbust and bust, compare the results with the brand’s sizing chart, and then evaluate the actual fit. A measurement chart can give you a useful starting size, but comfort, support, and cup shape ultimately matter just as much as the numbers.
