US Bra Size Calculator & Converter
Calculate your US bra size in inches, decode the DD/DDD/DDDD cup system, and convert instantly to UK, AU, EU & FR — with sister sizes and Victoria’s Secret, ThirdLove & Skims fit notes.
How to measure correctly
- Wear a non-padded bra or no bra for accurate readings.
- Underbust: wrap tape snugly around your ribcage directly under the bust. Keep tape parallel to the floor. Exhale fully and measure in inches.
- Overbust: measure around the fullest part of your bust. Tape should be loose enough to slide a finger underneath.
- Stand naturally — don’t lift arms or lean forward. Both measurements in the same posture.
- Round to the nearest ¼ inch (or 0.5 cm) for best accuracy.
International Size Conversions
Your Sister Sizes (Same Cup Volume)
Recommended Bras in Your Size
Top-rated US brands verified for sizing accuracy. Ships nationwide and internationally.
- US bands 30–46, cups A–DDD
- Seamless moulded cups
- Wacoal, Natori, ThirdLove styles
- US bands 32–46, cups DD–G
- Three-section cup, side support
- Elomi, Goddess, Wacoal styles
Measure in inches to get your accurate US bra size
What Is the US Bra Sizing System?
US bra sizing uses inch-based band numbers (28, 30, 32, 34, 36, 38…) paired with doubled-letter cup sizes (A, B, C, D, DD, DDD, DDDD). Band size is calculated from your underbust measurement in inches — 30 inches underbust equals a US 30 band. Cup size is the difference between your fullest bust and your underbust in inches, with each inch of difference representing one cup letter. The US system is used by Victoria’s Secret, ThirdLove, Skims, Savage X Fenty, Aerie, and Wacoal, and is the primary sizing reference for the world’s largest lingerie market.
The US bra sizing system is the most widely marketed but arguably the most confusing for international shoppers. It uses the same inch-based band numbers as the UK — US 34 and UK 34 are both built from the same underbust measurement — but diverges completely in cup letter notation above D cup.
While the UK assigns a unique letter to every cup size past D (E, F, FF, G, GG, H…), the US system doubles the letter D — creating DD, then DDD, then DDDD before switching to G. This means a US DDD cup and a UK E cup describe the exact same breast volume, but look nothing like each other on a label. This discrepancy trips up millions of shoppers every year when buying from international brands or retailers.
Band sizing in the US was historically calculated using an “add four or five inches” formula applied to the underbust measurement — a legacy from 1930s manufacturing that produced inaccurate results. Modern US brands and calculators (including this one) use the direct underbust-to-band method: your underbust in inches rounds to the nearest even number to give your band size, producing far more accurate fits.
US bands are inch-based — your underbust in inches rounds to the nearest even number.
US cup letters — the system uses DD, DDD, DDDD before switching to G, H, I at larger sizes.
- US bands are inch-based: 28, 30, 32, 34, 36, 38, 40, 42, 44, 46 — identical to UK band numbers
- US cups use doubled letters above D: DD, DDD, DDDD — then switch to G, H, I, J
- US DDD = UK/AU E = EU F — same cup volume, completely different label
- US 34 = AU 12 = EU 75 = UK 34 — all describe an underbust of 73–77 cm (28.5–30.5 in)
- Modern US calculators use the direct method: underbust in inches → band. No “add 4” offset.
How to Measure Your US Bra Size
You need two measurements: your underbust (ribcage below the bust) and your overbust (fullest part of the bust). Both measured in inches. A soft measuring tape is all you need.
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Prepare correctly
Wear a non-padded bra or no bra. Padded bras add 1–2 inches to your overbust reading, shifting your cup calculation by one or two letters. Stand naturally with arms relaxed.
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Measure your underbust in inches
Wrap the tape snugly around your ribcage directly beneath your bust. Keep it parallel to the floor all the way around. Exhale fully and read the measurement. Round to the nearest half inch. This gives your US band size: round to the nearest even number (if you get 31.5, your band is 32).
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Measure your overbust in inches
Measure around the fullest part of your bust. Keep the tape horizontal and loose enough to slide one finger underneath. Record to the nearest half inch.
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Calculate your US band
Your underbust in inches rounds to the nearest even number: 26–27 in = 26, 28–29 in = 28, 30–31 in = 30, 32–33 in = 32, 34–35 in = 34, 36–37 in = 36, 38–39 in = 38. If you measure an odd number like 33, try both 32 and 34.
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Calculate your US cup letter
Subtract underbust from overbust in inches: 1 in = A, 2 in = B, 3 in = C, 4 in = D, 5 in = DD, 6 in = DDD, 7 in = DDDD/G, 8 in = H, 9 in = I, 10 in = J. Each inch of difference = one cup step.
Remeasure every six months, or after any weight change of 5 lb (2.5 kg) or more, pregnancy, breastfeeding, or hormonal changes. Victoria’s Secret reports that 80% of their fitting appointments reveal the customer has been wearing the wrong size for over a year. A two-minute measurement prevents this entirely.
Skip the calculation — use the calculator
Enter your measurements once and get your exact US size plus conversions to UK, AU, EU, FR, and IT instantly.
Open the US Bra Size Calculator →US Bra Size Chart (Underbust Inch Reference)
This chart is the standard US sizing reference used by Victoria’s Secret, ThirdLove, Wacoal, and Nordstrom. It converts underbust inches to US band size and shows equivalents in UK, AU, EU, and FR systems.
US sizes compared with UK, AU, and EU systems
| US Band | Underbust (in) | Underbust (cm) | UK Band | AU Band | EU Band | FR Band |
|---|---|---|---|---|---|---|
| US 28 | 25–27 | 63–67 | 28 | AU 6 | 65 | 80 |
| US 30 | 27–29 | 68–72 | 30 | AU 8 | 70 | 85 |
| US 32 | 29–31 | 73–77 | 32 | AU 10 | 75 | 90 |
| US 34 | 31–33 | 78–82 | 34 | AU 12 | 80 | 95 |
| US 36 | 33–35 | 83–87 | 36 | AU 14 | 85 | 100 |
| US 38 | 35–37 | 88–92 | 38 | AU 16 | 90 | 105 |
| US 40 | 37–39 | 93–97 | 40 | AU 18 | 95 | 110 |
| US 42 | 39–41 | 98–102 | 42 | AU 20 | 100 | 115 |
| US 44 | 41–43 | 103–107 | 44 | AU 22 | 105 | 120 |
| US 46 | 43–45 | 108–112 | 46 | AU 24 | 110 | 125 |
US Cup to UK, AU, EU Cup Conversion
This is the single most confusing part of US bra sizing for international shoppers. The US uses doubled letters above D cup — DD, DDD, DDDD — before switching to single letters again. The UK, Australia, and EU all use different conventions for the same volumes. The table below maps every US cup to its international equivalent.
| US Cup | UK / AU Cup | EU Cup | JP / KR Cup | Overbust − Underbust (in) |
|---|---|---|---|---|
| AA | AA | AA | AA | ~0.5 in |
| A | A | A | A | 1 in |
| B | B | B | B | 2 in |
| C | C | C | C | 3 in |
| D | D | D | D | 4 in |
| DD | DD | E | E | 5 in |
| DDD | E | F | F | 6 in |
| DDDD / G | F | G | G | 7 in |
| G / H | FF | H | H | 8 in |
| H / I | G | I | — | 9 in |
| I / J | GG | J | — | 10 in |
| J / K | H | K | — | 11 in |
Many shoppers believe that Victoria’s Secret 34DDD is an unusually large cup. It is not. US DDD is equivalent to a UK/AU E cup and an EU F cup — a mid-range size stocked by every major UK and Australian specialist. The doubled-letter notation makes DDD appear extreme, but it represents only a 6-inch overbust-to-underbust difference. This myth causes D+ cup wearers to consistently underestimate their correct cup size.
What Are Sister Sizes in US Bras?
Sister sizes are US bra sizes that share the same cup volume but have different band widths. They are the most practical tool for shopping when your exact size is out of stock, or when a bra runs differently than the label suggests.
The sister size rule
- Smaller band, larger cup letter: If your 34D band rides up, try 32DD. Same volume, tighter band.
- Larger band, smaller cup letter: If your 34D band digs in, try 36C. Same volume, looser band.
| Size | Band Feel | Cup Volume | When to Try It |
|---|---|---|---|
| US 32DD | Tighter | Same | Your 34D band rides up or feels loose |
| US 34D | Standard | Same | Your primary size |
| US 36C | Looser | Same | Your 34D band digs in or feels tight |
Different breast shapes and fits across US bra brands
US Bra Brand Sizing Differences
Even within US sizing, brands grade their bands and cups differently. Here is how the major US and internationally-stocked brands run compared to the standard US chart.
Victoria’s Secret US
The most recognised US bra brand globally. VS uses standard US sizing on labels but tends to run small in the band and generous in the cup compared to the US standard. Stocks up to DDD cup in most styles, with limited G cup availability.
Fit: Bands run small — size up one band if your measurement falls between sizes. Cups run generous — your true size may be one cup smaller than VS recommends.
ThirdLove US
Known for half-cup sizing (e.g., 34B½, 36C½). ThirdLove bands run true to the US standard. Their extended cup range covers A–H cup in most bands. Half-cup sizes help wearers who fall between standard letters.
Fit: True to US band. If your ThirdLove cup gaps slightly, try the half-size down. If it overflows, try the half-size up.
Skims US
Kim Kardashian’s shapewear and bra label. Skims sizing generally follows the US standard with bands 30–46 and cups A–DDD. Their bralette sizing follows a different XS–3X system — check their size chart specifically for bralettes.
Fit: True to US size in underwire styles. Bralettes run one size small — size up from your usual.
Savage X Fenty US
Rihanna’s inclusive lingerie brand. Offers bands 32–46 and cups A–DDD (some styles up to G). Known for a wide range of skin-tone colourways and inclusive marketing. Sizing follows the US standard.
Fit: True to US size. Underwire styles fit true; their bralettes follow letter sizing (XS–4X) separate from the cup/band system.
Aerie US
American Eagle’s lingerie line. Stocks bands 30–44 and cups A–DDD. Known for soft-cup and wireless styles. Sizing follows the US standard with slightly softer bands than structured brands.
Fit: Bands run one size loose — size down if between sizes. Cups are true to US standard.
Wacoal US
Premium Japanese-American brand. Stocks bands 30–44 and cups A–G in their US line. Known for precise, consistent sizing. Wacoal’s US sizing follows the standard exactly and is considered the reference brand for US bra fit accuracy.
Fit: True to US size. The most consistent brand for accurate US sizing — use Wacoal as your benchmark when trying other brands.
Bravissimo UK (buying as US shopper)
UK specialist for D+ cups. Uses UK sizing — cup letters are identical to AU but band numbers use UK convention. If you’re US 34DDD, you would buy Bravissimo 34E. US cup letter shifts: DD→DD, DDD→E, DDDD→F.
Fit tip: Keep your US band number (34=34). Convert your cup: US DDD → UK E, US DDDD → UK F. Do not change the band number.
Calvin Klein US
Classic basics brand. Stocks bands 30–40 and cups A–DDD. Known for firm bands and slightly shallow cups. Limited range above DDD. Calvin Klein bands tend to run firm — many shoppers size up one band.
Fit: Bands run firm — size up one band if your measurement is on the border. Cups run slightly shallow — size up one cup for D and above.
Signs Your US Bra Size Is Wrong
Even with correct measurements, fit can vary between brands and shift over time. Here is how to read the signs and make adjustments.
Band size problems
- Band rides up at the back: band too big. Try one band down, one cup up (e.g., US 36C → 34D).
- Band leaves deep red marks or digs into ribs: band too small. Try one band up, one cup down (e.g., US 34D → 36C).
- Band pulls forward when you raise your arms: band too loose. Tighten hooks or size down one band.
- Straps falling off shoulders constantly: almost always a band issue, not a strap issue. A correctly fitting band carries 80% of support — straps are secondary.
Cup size problems
- Spillover at the top or sides of cup: cup too small. Size up one letter (e.g., US 34D → 34DD).
- Gaping or wrinkling fabric in cup: cup too big. Size down one letter (e.g., US 34D → 34C).
- Underwire sitting on breast tissue instead of flat on ribcage: cup too small. Size up one cup immediately.
- Centre gore not lying flat against sternum: cup too small or wire width wrong for your breast spacing.
Studies commissioned by US lingerie retailers consistently find that 80% of American women are wearing the wrong bra size — most are in a band that is too large and a cup that is too small. This is partly caused by the legacy “add 4 inches” formula, which artificially inflates band size. If you have not measured in the last 12 months, your current size is likely incorrect.
Why US Bra Sizing Confuses Everyone
US bra sizing is one of the most marketed systems in the world and yet produces more confusion per sale than almost any other. The reasons are structural, historical, and brand-driven.
The legacy “add four” formula
For decades, US bra fitting guides instructed women to measure their underbust in inches and then add four or five to get their band size. A woman with a 30-inch underbust would be told she wears a 34 band. This formula originated in the 1930s when bras used much stiffer fabrics that needed extra sizing. Modern stretch fabrics made the formula obsolete, but it persisted in retail fitting rooms until the 2000s, producing millions of women in bands two sizes too large and cups two sizes too small.
The doubled-letter ceiling problem
The US system’s decision to double the D letter — creating DD, DDD, DDDD — rather than introduce unique letters (as the UK did with E, F, FF, G) makes sizes above D visually alarming and practically ambiguous. “DDD” looks extreme to many shoppers, causing them to avoid it. Brands have responded by introducing alternative labels: some US brands call DDD a “G” or “E” internally, creating further confusion even within the same country’s labelling system.
The three-label problem for US shoppers
A US 34DDD shopper will encounter these labels when shopping internationally:
- 🇺🇸 Victoria’s Secret: 34DDD
- 🇬🇧 Bravissimo: 34E
- 🇩🇪 Triumph Germany: 75F
- 🇫🇷 Simone Pérèle: 90F
- 🇦🇺 Berlei: AU 12E
Our approach uses the direct underbust-to-band method — your underbust in inches rounds to the nearest even number, with no “add 4” offset. Cup size is the difference between overbust and underbust in inches. This produces the most anatomically accurate US bra size and eliminates the systematic over-banding error introduced by the legacy formula.
Shopping International Brands as a US Shopper
Buying from UK retailers
US and UK band numbers are identical — US 34 equals UK 34. For cups up to D, letters match exactly. Above D: US DD = UK DD, US DDD = UK E, US DDDD = UK F, US G = UK FF. Keep your band number the same and convert the cup letter using the table above. Bravissimo, ASOS, and Marks & Spencer all use UK labelling.
Buying from Australian retailers
AU cup letters are identical to UK cup letters — and therefore convert from US the same way as UK above. The only difference is the band: US 34 = AU 12, US 36 = AU 14, US 38 = AU 16. So US 34DDD = AU 12E. Australian retailers include Berlei, Bonds, and Bras N Things.
Buying from European retailers
EU uses centimetre bands. US 34 (underbust 73–77 cm) = EU 80. US 36 = EU 85. EU cup letters run higher than UK/AU above D: US DD = EU E, US DDD = EU F, US DDDD = EU G, US G = EU H. French brands (Chantelle, Simone Pérèle) add 15 to the EU band: US 34 = EU 80 = FR 95.
Always check the specific brand’s size chart before ordering internationally. US sizes are not universal even within the US — ThirdLove, Wacoal, and Victoria’s Secret all grade their bands and cups differently despite using the same US label convention. Read customer reviews that mention the reviewer’s usual size for the most reliable fit data.
Recommended Bras for US Sizing
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- US bands 30–46, cups A–DDD
- Wire-free all-day comfort
- Wacoal, Natori, Warners styles
- Smooth finish under any top
- Bands 30–42, cups A–DDD
- Maidenform, Wacoal, ThirdLove
- US bands 32–46, cups DD–G
- Underwire, three-section cup
- Elomi, Goddess, Wacoal Plus
- Encapsulation design for D–G cups
- US bands 30–44
- Panache Sport, Moving Comfort styles
Frequently Asked Questions
US bra sizing uses inch-based band numbers (28, 30, 32, 34, 36, 38…) and doubled-letter cup sizes (A, B, C, D, DD, DDD, DDDD, G, H). Band size is calculated from your underbust measurement in inches rounded to the nearest even number. Cup size is the difference in inches between your overbust and underbust: 1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD, 6 = DDD. Victoria’s Secret, ThirdLove, Wacoal, Skims, and Aerie all use this system.
US and UK band numbers are identical — US 34 equals UK 34. Cups match through D: US A = UK A, US D = UK D. Above D the systems diverge: US DD = UK DD, US DDD = UK E, US DDDD = UK F, US G = UK FF, US H = UK G. Keep your band number the same and convert only the cup letter. Brands like Bravissimo, Panache, and Freya use UK sizing. A US 34DDD shopper would look for UK 34E at Bravissimo.
US DDD is equivalent to UK/AU E cup and EU F cup. All three describe a bust-to-underbust difference of approximately 6 inches (15 cm). On a 34-inch band: US 34DDD = UK 34E = AU 12E = EU 75F = FR 90F. The physical cup volume is identical regardless of label. US DDD is not a large cup by global standards — it is a mid-range size well within the normal range stocked by specialist UK and Australian retailers.
Yes. Canada uses the same US sizing system — identical band numbers (30, 32, 34, 36) and identical cup letters (A, B, C, D, DD, DDD). Canadian brands like Knix and La Vie en Rose use US-style labelling. When buying from American retailers like Victoria’s Secret or ThirdLove, Canadian shoppers take the same size they would buy in Canada with no conversion needed. The only difference is that some Canadian stores also stock UK-labelled brands from European distributors, which use the UK cup system.
Both use US sizing but grade their bands and cups differently. Victoria’s Secret bands run small and cups run generous relative to the US standard — a VS 34D often fits like a Wacoal 36C or 34DD. Wacoal is considered the most consistent brand for true-to-size US fit. If you know your Wacoal size, you can use it as your benchmark when trying other brands. This brand-level variation is why measuring in inches and using a calculator is more reliable than relying on a brand’s self-reported size guide.
Sister sizes are US bra sizes with identical cup volume but different band widths. From US 34D, the sister sizes are 32DD (tighter band, same cup volume) and 36C (looser band, same cup volume). To find your US sister sizes, go up one band and down one cup letter, or down one band and up one cup letter. Sister sizes are especially useful at Victoria’s Secret, where popular sizes like 34C and 36B sell out quickly — knowing your sister sizes triples your options in any style.
Measure your underbust in inches snugly under your bust and round to the nearest even number — this gives your US band. Measure your overbust loosely at the fullest point. Subtract underbust from overbust in inches: 1 in = A, 2 in = B, 3 in = C, 4 in = D, 5 in = DD, 6 in = DDD. Home measuring is accurate within one sister size for approximately 85% of women when done without a padded bra. Our US calculator accepts both inches and centimetres.
The most commonly sold US bra sizes are 34B and 34C at mainstream retailers like Victoria’s Secret, Target, and Walmart. However, ThirdLove’s customer data — drawn from millions of bra fit quiz responses — suggests the true average US size is closer to 34DD or 36C when women measure accurately using the direct method. The discrepancy reflects the legacy “add 4” formula, which pushes many women into larger bands and smaller cups than their correct measurements indicate.
Every six months at minimum, or any time you experience weight change of 5 lb (2.5 kg) or more, pregnancy, breastfeeding, starting or stopping hormonal contraception, or noticeable changes in how your current bras fit. Victoria’s Secret, ThirdLove, and Nordstrom fitting specialists all recommend annual professional fittings or semi-annual self-measurement. Most American women have not measured in over two years — the primary reason 80% wear the wrong size.
If your underbust measurement falls on a boundary — for example, exactly 33 inches could be the top of a 32 band or the bottom of a 34 — try the smaller band first. US bra bands stretch with wear, particularly the cotton and elastane blends used by Victoria’s Secret, Aerie, and ThirdLove. A band that feels firm when new will relax to a comfortable fit within a week. If it still feels restrictive after several days of wear, size up to the next band.
Most mainstream US retailers (Victoria’s Secret, Aerie, Target) stock up to DDD or G cup in bands 30–44. Specialty US retailers like Nordstrom, Bare Necessities, and HerRoom stock extended ranges through N cup and band 54. International brands available in the US — Elomi, Goddess, Panache — extend to K or L cup in UK labelling, equivalent to approximately J or K in US notation. For very large sizes, shopping internationally from UK specialist retailers is often easier and more affordable than finding extended US sizing domestically.
US bra band sizes are based on inches — the band number approximates the underbust measurement in inches. Cup size is also calculated in inches: each inch of difference between overbust and underbust corresponds to one US cup letter. Our calculator accepts both inches and centimetres and converts internally. If you only have a centimetre tape measure, divide your cm measurement by 2.54 to get inches, or use the cm toggle in our calculator to get your US size directly from cm inputs.
ThirdLove introduced half-cup sizes (e.g., 34B½, 36D½) because standard US cup sizing uses 1-inch increments, which leaves many women between two whole cup sizes. A half-cup size represents 0.5 inches of additional cup volume — positioned between two standard letters. ThirdLove’s fit data from over 60 million women shows that approximately one-third of their customers fit best in a half-cup. If your current cup gapes slightly at the top or spills slightly at the sides, a half-cup size up or down may solve it without a full cup change.
Related Calculators & Guides
- Australian Bra Size Calculator
- UK Bra Size Calculator
- EU Bra Size Calculator
- India Bra Size Calculator
- Japan Bra Size Calculator
- All Country Calculators
- Global Bra Size Converter
- Free Bra Size Calculator
- Sister Size Calculator
- Cup Size Calculator
- Complete Bra Size Chart
- How to Measure Bra Size
- Common Bra Fit Problems
- Breast Shape Identifier
- AI Smart Fit Bra Calculator
- Cup Size Visual Guide
- Bra Fit Problem Solver
- How to Know If Your Bra Fits
- 34B Bra Size Guide
- 36C Bra Size Guide
- 32C vs 34B Sister Size Guide
- 34D vs 36C Comparison
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