bra-calculator.com ยท Prestige Edition 2026

The Definitive Bra Size Chart Calculator
Intelligence Chart & Sister Size Tool

Interactive grid ยท Sister sizes ยท International conversions ยท
Volume analysis ยท Brand fit variance ยท Body shape logic

15 Cup Sizes 13 Band Sizes 5 Regions 12 Brands Smart Q&A
Try: "sister sizes 32F" ยท "compare 34D and 36C" ยท "36DD in UK"
Region
Overlay
Selected
Sister size
Same volume
US Size
34DD
Band 34" ยท DD Cup ยท Medium-Large
International Equivalents
Sister Sizes
Click any sister size to select it in the grid
Cup Volume
0%
โ€”
Score: โ€”
AABDFHK
Shape Guide
Brand Fit Notes
Common Questions

Compare Two Sizes

Enter any two bra sizes to analyse cup volume, band difference, and sister-size relationship.

vs

Volume Scale

Visual representation of cup volume at a fixed band. Click any bar to jump to that size in the grid.

Fixed band

Brand Fit Guide

How major lingerie brands run relative to your measured size. Always verify against the brand's own size chart.

Bra Size ChartCalculator FAQs

Sizing is a guide only. Fit varies by brand, fabric, and body shape.
Bra Calculator Bikini Calculator Sister Sizes
โ€” Size Intelligence Guide โ€”
0+
Unique sizes 13 bands ร— 15 cups on the full grid
5
Global regions US ยท UK ยท EU ยท AU ยท JP
0
Brand profiles Fit variance from real brands
0
Max volume score 52K โ€” largest charted size
How It Works

Not a size converter.
A sizing intelligence system.

Every bra size carries two components: a band number (your ribcage measurement) and a cup letter (the difference between bust and band). Together they define cup volume โ€” but the letter alone tells you almost nothing. A DD cup on a 34 band is not the same volume as a DD on a 38 band. Volume scales with band size. This chart makes that relationship visible, measurable and interactive.
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Sister sizes โ€” see every equivalent volume across bands, AAโ€“K, 28โ€“52
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Volume scoring โ€” compare cup volume beyond cup letters alone
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International conversion โ€” US, UK, EU, AU, JP with accurate band mapping
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Projection guide โ€” shallow, average and projected breast shape logic
โ—†
Brand variance โ€” how 12 major brands run vs your measured size
BAND SIZE BUST MEASUREMENT CUP volume diff BAND ribcage UNDERWIRE
Sister Size Logic

Different number.
Same volume.

Sister sizes share an identical cup volume across different band widths. Use our sister size calculator to explore the full chain for any size. Click a size below to learn the fit strategy.
All four sizes carry equal cup volume
32Evol: 128
Tighter band
โ†’
34DDvol: 170
Measured size
โ†’
36Dvol: 144
Looser band
โ†’
38Cvol: 114
Widest band
Click any size above to see the fit strategy. All sister sizes share the same cup volume โ€” the difference is band width and support level. A snugger band gives more lift; a looser band gives more comfort.
Rule One Up 1 band = Down 1 cup Going from 34 to 36 band? Drop one cup letter (DD โ†’ D). Volume stays identical.
Rule Two Down 1 band = Up 1 cup Going from 34 to 32 band? Increase one cup letter (DD โ†’ E). Same cup volume.
Rule Three Band = the support source 80% of support comes from the band, not the straps. A snug band is always the priority.
D cup volume across band sizes
28″D
28D ยท 112
112
32″D
32D ยท 128
128
34″D
34D โ† avg ยท 136
136
36″D
36D ยท 144
144
38″D
38D ยท 152
152
42″D
42D ยท 168
168
46″D
46D ยท 184
184
52″D
52D ยท 208
208
Key insight: A 52D has 85% more cup volume than a 28D โ€” despite sharing the same letter “D”.
Volume Scaling

“D cup”
is not one size.

The most common misconception in bra sizing: the cup letter defines a fixed volume. It doesn’t. Cup volume is the product of both band and cup together. A 28D has a volume score of 112. A 52D has a score of 208. Same letter. Completely different volume. Our bra size calculator accounts for this precisely.
This is why cup letters alone can’t be used for comparison. When someone says they’re “a D cup,” that describes a ratio โ€” not an absolute volume. Context is everything.
Volume scores let you compare any two sizes, find true sister sizes, and understand why a 36C and a 34D can look completely different on different bodies.
International Sizing

One size.
Five naming systems.

The same body, the same fit โ€” completely different numbers. Here’s how 34DD translates globally. Shopping international brands like Freya or Wacoal? This matters.
๐Ÿ‡บ๐Ÿ‡ธUnited States34DDBand: inches ยท Cup: double letters (DD, DDD)
๐Ÿ‡ฌ๐Ÿ‡งUnited Kingdom34DDBand: inches ยท Cup: FF, GG in extended range
๐Ÿ‡ช๐Ÿ‡บEurope / France75EBand: centimetres ยท Cup: DD = E (single letters)
๐Ÿ‡ฆ๐Ÿ‡บAustralia34DDBand: inches ยท Cup: matches UK/US most brands
๐Ÿ‡ฏ๐Ÿ‡ตJapan75DBand: centimetres ยท Cup: different increments
Band conversions: US/UK band ร— 2.54 โ‰ˆ EU band (e.g. 34″ = EU 75). Cup ladders vary by brand above DD. Always check the brand’s own chart when ordering internationally โ€” use our conversion tool to confirm.
Shape Intelligence

Volume is only
half the equation.
Shape matters too.

Two women with identical measurements can need completely different cups because breast tissue distributes differently. Projection โ€” how far tissue extends from the chest wall โ€” is the variable most charts ignore entirely.
โ—ฏ
Shallow ProjectionTissue is wide and flat. Best with demi, balconette, or t-shirt styles. Avoid deep plunge cups where excess fabric appears at the top.
โ—‘
Average ProjectionWorks with most standard styles. Full cup, balconette, and plunge cuts all generally fit well at your size.
โ—
Projected ProjectionTissue is deeper than wide. Needs greater cup depth. Shallow moulded cups will gap at the top despite correct volume.
chest depth SHALLOW wide ยท low depth
Brand Architecture

Fit is structural.
Not numerical.

Same size label. Completely different fit. Here’s how six major brands compare in band and cup construction โ€” see the full brand guide in the tool above.
Band
Cup Depth
Best For
๐ŸŒธ Victoria’s Secret
 Runs loose (+1โ€“2″)
 Shallow
Aโ€“D cups, fashion
โœฆ Freya
 True to size
 Generous depth
Dโ€“K, projected
โ—ˆ Skims
 Runs tight (size up)
 Shallow/soft
Aโ€“C, lounge
โŠ• Wacoal
 True to size
 True depth
Aโ€“H, consistent
๐ŸŒฟ Chantelle
 EU sizing
 Generous
Aโ€“H, full-on-top
โ—‘ ThirdLove
 True to size
 Half sizes
Aโ€“H, in-between
True to size
Runs larger
Runs smaller
EU sizing (convert)
Sizing is a starting point. Fit is architecture. The same 34DD can behave as a 34C in one brand and a generous 34E in another. Brand fit notes eliminate online shopping guesswork.
Who It’s For

Built for every stage
of the fitting journey.

๐Ÿ”„Between SizesUnsure whether to go up or down? Sister sizing gives you a precise alternative โ€” same volume, better comfort.
๐ŸŒInternational ShoppersShopping Freya (UK), Wacoal (JP), or Chantelle (EU)? This chart converts your bra size accurately into every system.
๐Ÿ“Size Re-EvaluationPost-pregnancy, post-weight change, or first-time fit check โ€” the volume system shows exactly where you land on the grid.
๐Ÿท๏ธOnline Bra ShoppingCan’t try it on? Brand fit notes tell you how each brand runs โ€” order the right size first time and avoid costly returns.
โš–๏ธSize ComparisonIs 34DD bigger than 36D? Our compare tool answers instantly with exact volume scores and percentage differences.
๐Ÿ‘™Swimwear & BralettesCup equivalents don’t always translate. Use our bikini top calculator alongside this chart to find your swim equivalent.
BAND SIZE BUST SIZE 80% support = band 20% support = straps
Measurement Science

Band, cup &
projection explained.

Understanding how each dimension contributes to fit eliminates guesswork when shopping online or switching brands.
1
Band Size โ€” The FoundationMeasured snugly around the ribcage directly under the bust. Provides 80% of all bra support. Should feel firm, sit parallel to the floor and not ride up at the back. If the band rides up, it’s too loose โ€” not too tight.
2
Cup Size โ€” The DifferenceThe numerical difference between bust and band measurements. Each inch = one cup size. But volume scales with band โ€” a D on 34 is not the same as a D on 38. Use our volume tool to compare exactly.
3
Projection โ€” The Missing VariableHow far tissue projects from the chest wall. Shallow shapes need wider, shallower cups. Projected shapes need depth. Getting this wrong causes the most common fitting problems โ€” gaping at the top or overflow at the bottom wire.
Related Calculators

More tools to
perfect your fit.

๐Ÿ“ Bra Size Calculator Enter your measurements to find your exact size across all regions and brands. ๐Ÿ”„ Sister Size Calculator See every sister size for any bra size in seconds. Tighter band, same volume. ๐Ÿ‘™ Bikini Top Calculator Convert your bra size to swimwear. Swim sizing follows different rules โ€” this handles it. โš–๏ธ Size Comparison Tool Is 34DD bigger than 36D? Compare any two sizes by exact cup volume percentage. ๐Ÿ“Š Volume Scale Visual cup volume chart for AA through K at any fixed band. See exactly how volume grows. ๐Ÿท๏ธ Brand Fit Guide How Victoria’s Secret, Freya, Wacoal, ThirdLove and others run vs your measured size.
“

When you understand volume logic,
sizing confusion disappears.

bra-calculator.com ยท Prestige Intelligence Edition 2026
Sizing Principle Sizing is a starting point.
Fit is architecture.
Volume Principle Cup letters describe a ratio.
Not an absolute volume.
Sister Size Principle Different numbers.
Identical volume.

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