Your bra size consists of two components: a band size (the number) and a cup size (the letter). The band size is your underbust measurement, while the cup size is determined by the difference between your bust and underbust measurements.

To find your bra size:

1. Measure your underbust (this becomes your band size)

2. Measure your bust at the fullest point

3. Subtract band from bust to determine cup size

For example, if your underbust is 32 inches and your bust is 36 inches, the 4-inch difference means you're a D cup—so your size is 32D.

Use our free bra size calculator above for instant, accurate results. Simply enter your measurements and get your UK, EU, and US sizes in seconds.

The most accurate way to know your bra size is to measure yourself at home using a soft measuring tape. Follow these simple steps:

Quick Method

1. Underbust measurement = your band size

2. Bust measurement (fullest part) minus band size = cup size difference

3. Use the cup size chart to convert the difference to a letter

Signs you're wearing the wrong bra size:

• Band rides up at the back

• Cups gap or overflow at the top

• Breast tissue spills out at the sides

• Straps constantly dig into your shoulders

• You need to adjust your bra throughout the day

If you're experiencing any of these issues, it's time to remeasure. Our AI-powered bra size calculator provides professional accuracy in under 60 seconds.

Bra sizes extend far beyond the commonly known DD cup. At sloggi, we offer an extensive size range so everyone can find their perfect fit:

Our Size Range:

• UK cup sizes: Up to K cup

• Band sizes: 28-44 inches (60-100cm EU)

Common large cup sizes include: DD, E, F, FF, G, GG, H, HH, J, JJ, K

Important features for larger cup sizes:

• Wide, cushioned straps to distribute weight

• Reinforced underwire for enhanced support

• Multi-hook back closures for secure fit

• Side support panels to prevent spillage

Remember, cup size is relative to band size. A 32DD has a different volume than a 38DD, which is why accurate measurement of both dimensions is crucial. Use our calculator to find your exact size, whatever your cup size.

Measuring your bra size at home is simple and takes just a few minutes. Here's exactly what to do:

What You Need:

• Soft fabric measuring tape (not rigid metal)

• Mirror (helpful but optional)

• Someone to help (optional but can improve accuracy)

Step-by-Step Home Measurement:

1. Wear the right bra: Put on a non-padded, well-fitting bra or no bra at all

2. Measure band size: Wrap tape snugly around your ribcage, just under your breasts. Keep it level and parallel to the floor

3. Measure bust size: Measure around the fullest part of your bust, usually at nipple level

4. Calculate cup size: Subtract band measurement from bust measurement

Pro Tips for Accuracy:

• Stand in front of a mirror to ensure tape is level

• Don't hold your breath while measuring

• Don't pull the tape too tight, it should be snug but comfortable

• Take measurements 2-3 times to confirm consistency

• Measure at the same time of day (bust size can fluctuate)

Our detailed measuring guide above includes visual aids and a step-by-step calculator to help you get precise measurements every time. And remember, not everyone who wears a bra identifies in the same way—this guide is here for every body.

Cup size represents the volume difference between your bust and band measurements. Each cup letter corresponds to a specific difference in inches or centimeters.

How Cup Sizes Work:

• Each cup size = approximately 1 inch (2.5cm) difference

• A cup = 1" difference

• B cup = 2" difference

• C cup = 3" difference

• D cup = 4" difference

• DD/E cup = 5" difference

• And so on...

Real Example:

• Band measurement: 34 inches

• Bust measurement: 37 inches

• Difference: 3 inches = C cup

• Your bra size: 34C

Important to Know:

Cup size is NOT absolute—it's relative to your band size. This means:

• A 34C has a different cup volume than a 36C

• A 34C and 36B have the same cup volume (sister sizes)

• Both measurements work together to determine fit

This is why you need to measure both your band and bust to find the bra size that truly fits you. Our calculator does all the math for you automatically.

UK bra sizes follow a specific format: [Band Number][Cup Letter]

UK Sizing System Explained:

Band sizes:

Even numbers from 28 to 44+ (28, 30, 32, 34, 36, 38, 40, 42, 44)

Cup sizes:

AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K

Key Differences Between Sizing Systems:

UK vs US:

• Band sizes are similar but cup letters differ after D

• UK DD = US E cup

• UK E = US DDD or F cup

• Generally UK sizing is more consistent

UK vs EU:

• EU uses centimeters for band size

• UK 32 = EU 70

• UK 34 = EU 75

• UK 36 = EU 80

• Cup letters generally match between UK and EU

To find your accurate UK bra size, use our calculator tool above. It automatically converts between UK, US, and EU sizing so you can shop confidently from any brand or region.

If you prefer metric measurements, here's how to measure your bra size in centimeters:

Band Size (cm):

1. Measure your underbust in centimeters

2. Round to the nearest 5cm increment

3. Common EU band sizes: 60, 65, 70, 75, 80, 85, 90, 95, 100cm

Bust Measurement (cm):

1. Measure around the fullest part of your bust in centimeters

2. Keep the tape level and snug but not tight

Calculate Cup Size:

Subtract band measurement from bust measurement:

Difference (cm) Cup Size

10-12cm - A

12-14cm - B

14-16cm - C

16-18cm - D

18-20cm - DD/E

20-22cm - F

22-24cm - FF

24-26cm - G

Example Calculation:

• Band: 75cm

• Bust: 91cm

• Difference: 16cm = C cup

• Your size: 75C (EU) or 34C (UK)

Our bra size calculator works with both inches and centimeters. Simply select your preferred unit of measurement and enter your numbers for instant results.

Sister sizes are different bra sizes that have the same cup volume. When you go up one band size, you go down one cup size to maintain the same volume (and vice versa).

How Sister Sizes Work:

If you wear a 34C, your sister sizes are:

• 32D (smaller band, larger cup letter)

• 36B (larger band, smaller cup letter)

All three sizes (32D, 34C, 36B) have the same cup volume, but the proportions and fit feel different due to the band size.

When to Use Sister Sizes:

• Band too tight? Try the next band size up + one cup size down

• Band too loose? Try the next band size down + one cup size up

• Your size is out of stock? Sister sizes are often available

• Between sizes? Sister sizing helps fine-tune your fit

Sister Size Chart Examples:

Your Size

Smaller Band

Larger Band

32C

30D

34B

34D

32DD

36C

36DD

34E

38D

38E

36F

40DD

Important Note: While sister sizes have the same cup volume, they fit differently around your body. The band provides most of the support, so getting the right band size is crucial for comfort and proper lift. If you're between sizes, always try both options to see which feels better.

The average bra size in the UK has changed significantly over the past few decades. Current statistics show that the average UK bra size is approximately 36D.

UK Bra Size Trends:

• 1950s average: 34B

• 1990s average: 34C

• 2010s average: 36C

• Current average: 36D

Why Has the Average Changed?

Several factors contribute to the increasing average:

• Improved measuring techniques and awareness

• Better access to proper bra fittings

• Changes in lifestyle and nutrition

• Greater availability of larger cup sizes

But Averages Don't Tell Your Story:

Every body is unique. The "average" size doesn't mean it's the "right" size for you. Factors that influence your bra size include:

• Genetics and body type

• Weight fluctuations

• Pregnancy and breastfeeding

• Age and hormonal changes

• Overall health and fitness

And not everyone who wears a bra identifies in the same way, instead of comparing yourself to statistics, focus on finding YOUR perfect fit. Our bra size calculator is designed to give you accurate, personalized measurements regardless of what the average might be.

The number in your bra size represents your band size—the measurement around your ribcage directly under your breasts.

Understanding Band Size Numbers:

UK/US Band Sizes:

• Numbers represent inches around your underbust

• Always even numbers: 28, 30, 32, 34, 36, 38, 40, 42, 44

• Example: Size 34D means 34-inch underbust, D cup

EU Band Sizes:

• Numbers represent centimeters around your underbust

• Increments of 5cm: 60, 65, 70, 75, 80, 85, 90, 95, 100

• Example: Size 75C means 75cm underbust, C cup

Why Band Size Matters:

The band provides 80-90% of your bra's support—not the straps! A correctly fitted band should:

• Sit level all the way around (not ride up at the back)

• Feel snug but not restrictively tight

• Stay in place when you move

• Allow you to fit two fingers underneath comfortably

Common Band Size Mistakes:

• Wearing band too loose (causes lack of support)

• Wearing band too tight (causes discomfort and bulging)

• Not adjusting band as weight changes

The band is the foundation of proper bra fit. Get this measurement right first, then determine your cup size. Our calculator helps you get both dimensions accurately.