B Swim Black Out Katia Bikini Top
B Swim Black Out Katia Bikini Top - XS / BLAOU / U673 On backorder — ships as soon as available
About this style
About this style
Double front keyholes make this bralette top both flirty and adjustable. The underbust band gives the Katia a crop length and provides a little more coverage. Shoulder straps are fully adjustable for a secure fit.
- Bralette
- Removable Cups
- Adjustable Straps
- Soft Underbust Band
- Double Front Adjustable Keyholes
- Front Spaghetti Tie Closure
- Crop Top
- Minimal Coverage
- Bottom Sold Separately
Fabric Content: 78% Nylon, 22% Spandex
Delivery Details
Delivery Details
- Ships in 1–3 business days
- Free U.S. shipping on orders $50+
- Standard shipping (5–7 business days)
- Expedited shipping (2–4 business days)
- Tracking details emailed once your order ships
- Worldwide shipping available
Returns & Exchanges
- Easy 30-day returns
- Discreet packaging on all orders
- View full Shipping & Returns Policy
- Measure two things: your band (snug under the bust) and your bust (across the fullest point).
- Subtract band from bust. Each inch of difference is one cup letter — 1″ A, 2″ B, 3″ C, 4″ D, 5″ DD.
- Pair your band number with your cup letter. A 32″ band with a 36″ bust is a 32D.
- A cup letter is a difference, not a fixed volume — a 32D and a 36D are different cup sizes.
- Between sizes? Use a sister size — same cup volume, one band over.
- Re-measure every 6–12 months. Brand fit varies; treat the chart as a starting point.
How to Measure Your Bra Size
Two measurements with a soft tape, basic subtraction, a moment to interpret — about five minutes. Measure over a thin, unlined bra (or no bra for the band), and keep the tape parallel to the floor.
Wrap the tape snugly around your ribcage directly under the bust, parallel to the floor, on the exhale. Round to the nearest even inch — bands come in even sizes only (28, 30, 32, 34…).
Wearing an unlined, non-padded bra, wrap the tape around the fullest point of the chest, parallel to the floor, snug but not compressing. For a C cup and above, lean to 90° while measuring.
Bust minus band, in inches. Each inch of difference is one cup letter: 1=A, 2=B, 3=C, 4=D, 5=DD, 6=DDD/F, 7=G. Round to the nearest whole inch.
Pair your band number with your cup letter. A 33″ band (rounds to 32) with a 36″ bust (4″ difference) gives a 32D. A 36″ band with a 39″ bust gives a 36C.
Older guides told you to add four inches to your underbust to find the band. Don't. Modern band elastic is engineered for the direct underbust measurement — adding inches creates a too-loose band, the leading cause of bra mis-fit.
For the full step-by-step with troubleshooting, see how to measure your bra size at home.
The Master US Bra Size Chart
Find your underbust measurement down the left column, then read across to your bust measurement. Where they meet is your size. The row gives you the band; the cup letter is the bust-to-band difference.
| Underbust (Band) | A (+1″) | B (+2″) | C (+3″) | D (+4″) | DD (+5″) | DDD/F (+6″) | G (+7″) |
|---|---|---|---|---|---|---|---|
| 28″ | 28A · 29″ | 28B · 30″ | 28C · 31″ | 28D · 32″ | 28DD · 33″ | 28DDD · 34″ | 28G · 35″ |
| 30″ | 30A · 31″ | 30B · 32″ | 30C · 33″ | 30D · 34″ | 30DD · 35″ | 30DDD · 36″ | 30G · 37″ |
| 32″ | 32A · 33″ | 32B · 34″ | 32C · 35″ | 32D · 36″ | 32DD · 37″ | 32DDD · 38″ | 32G · 39″ |
| 34″ | 34A · 35″ | 34B · 36″ | 34C · 37″ | 34D · 38″ | 34DD · 39″ | 34DDD · 40″ | 34G · 41″ |
| 36″ | 36A · 37″ | 36B · 38″ | 36C · 39″ | 36D · 40″ | 36DD · 41″ | 36DDD · 42″ | 36G · 43″ |
| 38″ | 38A · 39″ | 38B · 40″ | 38C · 41″ | 38D · 42″ | 38DD · 43″ | 38DDD · 44″ | 38G · 45″ |
| 40″ | 40A · 41″ | 40B · 42″ | 40C · 43″ | 40D · 44″ | 40DD · 45″ | 40DDD · 46″ | 40G · 47″ |
| 42″ | 42A · 43″ | 42B · 44″ | 42C · 45″ | 42D · 46″ | 42DD · 47″ | 42DDD · 48″ | 42G · 49″ |
| 44″ | 44A · 45″ | 44B · 46″ | 44C · 47″ | 44D · 48″ | 44DD · 49″ | 44DDD · 50″ | 44G · 51″ |
Format: size · bust measurement in inches. Read left to right — a 32″ underbust with a 36″ bust = 32D.
Bra Cup Sizes Explained
The single most misunderstood thing on any bra chart: a cup letter is not a fixed volume. It's the difference between your bust and your band. That's why a 32D and a 36D are not the same cup size — the 36D holds more, because it sits on a bigger band. The cup-size chart below shows what each difference means.
| Bust − Band | US Cup | What it means |
|---|---|---|
| 1″ | A | One inch of projection beyond the ribcage. |
| 2″ | B | The most common starting estimate — often too small once the band is corrected. |
| 3″ | C | The most-shopped cup overall. See C cup size explained. |
| 4″ | D | Last cup that's identical across US, UK, and EU systems. |
| 5″ | DD | Where US and UK sizing begins to diverge. See DD cup size explained. |
| 6″ | DDD / F | US doubles up (DDD); UK and EU continue the alphabet. |
| 7″ | G | Full-bust territory — band fit matters most here. |
Because the cup is a difference and not an absolute, two bras with the same letter on different bands hold different amounts. This is the whole basis of sister sizing — and why the size on your old bra is a poor guide to a new brand.
Sister Size Reference
Sister sizes share the same cup volume on a different band. They solve the most common mis-fit pattern (band wrong, cup right) and roughly triple your shopping range. Going up one band and down one cup letter gives a looser-band sister; going down one band and up one cup gives a tighter-band sister. (For the deep dive, see sister sizes explained.)
| Sister Down (tighter band, larger cup) | Your Size | Sister Up (looser band, smaller cup) |
|---|---|---|
| 30D | 32C | 34B |
| 30DD | 32D | 34C |
| 32C | 34B | 36A |
| 32D | 34C | 36B |
| 32DD | 34D | 36C |
| 32DDD | 34DD | 36D |
| 34C | 36B | 38A |
| 34D | 36C | 38B |
| 34DD | 36D | 38C |
| 36D | 38C | 40B |
| 36DD | 38D | 40C |
International Sizes at a Glance
Shopping a UK, European, or Japanese brand? Cup letters match through D, then diverge — and bands switch from inches to centimeters. Here's the quick view for the most common sizes; the full country-by-country charts, the cm conversions, and an interactive converter live on the conversion page.
| US | UK | EU | FR / ES | AU / NZ | JP |
|---|---|---|---|---|---|
| 32C | 32C | 70C | 85C | 10C | 70C |
| 34C | 34C | 75C | 90C | 12C | 75C |
| 34D | 34D | 75D | 90D | 12D | 75D |
| 34DD | 34DD | 75E | 90E | 12DD | 75E |
| 36C | 36C | 80C | 95C | 14C | 80C |
| 36D | 36D | 80D | 95D | 14D | 80D |
"A size chart is a starting point. Brand grading varies, body shapes vary, the same labeled size fits differently across pieces. Use the chart as a hypothesis — and use sister sizing to test it without committing to a wrong number."
— HauteFlair Fit Editorial Team
Frequently Asked Questions
How do I read a bra size chart?
How do I measure my bra size at home?
What do the cup sizes on a bra chart mean?
What is a sister size on a bra chart?
Should I trust the size on my current bra?
How often should I re-measure my bra size?
Is the +4 method for finding my band size accurate?
Do all brands match the same size chart?
This page is for informational and educational purposes only. HauteFlair is not responsible for individual fit outcomes — bra sizing varies between brands and styles, and the figures in this chart reflect industry-standard grading, not contractual mappings. For best results, refer to each brand's specific size chart. Last reviewed: June 4, 2026.
B Swim Black Out Katia Bikini Top
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