How Big Are KK Cups? KK Breast Size, Volume & Measurements
KK cups are part of the extended UK bra sizing system and appear directly after K in the cup size sequence. Many women searching how big are KK cups want to understand the bust difference, cup volume and where this size sits within the UK bra sizing progression.
This guide includes simplified visual diagrams showing how KK cup volume changes across different UK band sizes, alongside examples comparing nearby cup sizes.
To see how this size compares across all fuller-bust sizes, view our bra cup size guide.
Is a KK cup bra big? In the UK bra sizing system, KK cups are part of the fuller-bust range, although the overall size depends on the band measurement.
A KK cup in the UK bra sizing system sits between K and L. It typically represents about a 16 inch difference between the bra band size and the fullest bust measurement.
The typical progression around this size is: JJ → K → KK → L.
Many people search to understand how big KK cups are because cup letters alone do not show the full picture. In bra sizing, the band size and cup size work together, which means a 30KK, 34KK and 40KK all have different cup volumes.
If you are unsure of your starting size, you can begin with our Bra Size Calculator, confirm the fit using our Bra Fitting Advice, and compare sizes across brands using our Bra Size Converter.
KK Cup Bra Size Examples by Band Size
These simplified diagrams show how a KK cup can look different across band sizes. A cup letter does not represent one fixed breast volume, so a 30KK, 34KK, 38KK and 42KK all increase in overall cup volume as the band size increases.
30KK
34KK
38KK
42KK
These images are simplified educational diagrams designed to show relative cup volume. Individual breast shape, body shape and bra style can all affect how a size appears in real life.
The KK cup letter stays the same, but the overall cup volume increases as the band size increases. This is why a 42KK represents more breast volume than a 30KK.
How KK Cups Compare With Nearby Cup Sizes
Many people searching how big are KK cups also compare this size with nearby cup sizes such as K and L. These simplified diagrams help show how cup volume increases across the UK bra size sequence.
34K
34KK
34L
These images are simplified educational diagrams designed to show relative cup volume progression across nearby UK cup sizes.
Cup volume increases gradually across the UK bra sizing system. A 34L has noticeably more overall cup volume than a 34K, with 34KK sitting between the two.
Best Bras for KK Cups (Supportive Everyday Styles)
If you wear a KK cup, many women look for styles designed to provide support, structure and everyday comfort across a range of band sizes. The bras below are commonly selected in KK cup sizes.
If you are shopping for KK cup bras, checking your band size first is important because a 32KK, 36KK and 40KK all represent different overall cup volumes.
As an Amazon Associate I earn from qualifying purchases.
You can explore more options in our KK Cup Bras guide.
Many women try to understand how big KK cups are, but cup letters alone do not represent a fixed breast size. Bra sizing works by combining the band size with the cup size, meaning a 32KK, 36KK and 40KK all have different cup volumes.
If you are unsure of your starting size, you can begin with our Bra Size Calculator, confirm the fit using our Bra Fitting Advice, and compare sizes across brands using our Bra Size Converter.
How Big Are KK Cups in the UK Cup Size Sequence?
The UK bra sizing system includes several double-letter cup sizes which create smaller steps between cup volumes.
J → JJ → K → KK → L
Each step represents roughly a 1 inch increase in the difference between the bra band size and the fullest bust measurement.
KK is one of the double cup sizes used in the UK bra sizing system. These additional cup sizes create smaller increments between larger cup volumes and help improve bra fit across fuller-bust sizes. You can learn more about how this system works in our Double Cup Bra Sizes Explained guide.
You can see the full sequence in our UK Bra Cup Size Chart.
For context, many people researching how big are KK cups also compare this size with neighbouring cups such as K, L and LL, which represent the surrounding steps in the UK bra sizing progression.
You can explore how all fuller-bust sizes progress in our bra cup size guide.
A cup letter does not represent one fixed breast size. For example, a 30KK has a smaller cup volume than a 36KK because cup size increases as the band size increases.
Examples Showing How Big KK Cups Are Across Band Sizes
The bust measurement for a KK cup changes depending on the band size. These examples help explain how big are KK cups across different band measurements and how the same cup letter appears across several sizes.
| Bra Size | Approx Bust Measurement |
|---|---|
| 32KK | 48 inches |
| 34KK | 50 inches |
| 36KK | 52 inches |
| 38KK | 54 inches |
Because cup size changes with band size, a KK cup can appear different depending on the band measurement. For example, a 34KK has a similar cup volume to its sister sizes 32L and 36K. You can learn more about how these equivalent sizes work in our Bra Sister Sizes Explained guide.
How Big Are KK Cups? Estimated Volume and Weight by Band Size
Many people searching how big are KK cups want to understand the approximate breast volume or weight this size represents. Because cup volume increases with band size, the overall breast size of a KK cup varies depending on the band measurement.
The estimates below illustrate how KK cup volume can increase across common band sizes.
| Bra Size | Approx Cup Volume | Approx Weight (Both Breasts) |
|---|---|---|
| 32KK | ~1750 cm³ | ~3.2 kg / 7.1 lb |
| 34KK | ~1880 cm³ | ~3.4 kg / 7.5 lb |
| 36KK | ~2030 cm³ | ~3.7 kg / 8.2 lb |
| 38KK | ~2190 cm³ | ~4.0 kg / 8.8 lb |
| 40KK | ~2360 cm³ | ~4.3 kg / 9.5 lb |
| 42KK | ~2550 cm³ | ~4.6 kg / 10.1 lb |
Looking at these examples helps explain how big are KK cups across different band sizes and why a KK cup on a smaller band will have less overall volume than the same cup letter on a larger band.
Best Bras for 34KK (Top Picks for Everyday Support)
If you wear a 34KK, these bras are commonly chosen for their supportive structure, balanced fit and everyday comfort.
What Is a KK Breast Size?
A KK breast size refers to the cup volume created when the difference between the bra band size and the fullest bust measurement is roughly 16 inches in the UK bra sizing system.
Some people searching online may refer to this informally as a KK boob size. In professional bra fitting, however, cup size is determined by the difference between the bra band size and the bust measurement, rather than a fixed breast size.
Because cup size changes with band size, a 30KK, 34KK and 40KK all represent different breast volumes even though the cup letter is the same. This is why bra sizing always combines both the band size and cup size.
Some people also describe this size informally as a KK boob size, but in bra fitting the correct measurement refers to the difference between the band and bust measurements rather than a fixed breast size.
If you are looking for bras in this size, you can explore guides such as best bras for 34KK, best bras for 36KK and best bras for 38KK.
Explore KK Cup Guides
Related Bra Size Guides
- Double Cup Bra Sizes Explained
- J vs JJ vs K Cup Size Comparison
- K vs KK vs L Cup Size Comparison
- Bra Sister Sizes Explained
Cup sizes increase gradually in the UK bra sizing system. You can also explore nearby cup sizes to understand how volume progresses:
How Big Are KK Cups? Common Questions
Yes. In the UK bra sizing system the sequence progresses K → KK → L, meaning a KK cup is one size larger than K.
A KK cup typically represents about a 16 inch difference between the bra band size and the fullest bust measurement. The actual breast size varies depending on the band size because cup volume increases as band size increases.
KK cups are part of the extended UK bra sizing system and are generally considered a fuller-bust size. However, the overall size still depends on the band measurement.
A KK cup can look different depending on the band size. For example, a 30KK has less overall cup volume than a 42KK. The diagrams on this page provide simplified educational examples showing how KK cup volume changes across different UK band sizes.
For additional background on bra cup volume and weight estimates, you may also find this bra size reference on Wikipedia helpful alongside the guides on this site.
Find Your Correct Bra Size
If you are unsure which size to try, measure your bust and band using our Bra Size Calculator.
You can then confirm your fit using our Bra Fitting Advice and compare sizes across brands using the Bra Size Converter.