US Bra Size Calculator
American bra sizing is straightforward to calculate but frustrating to shop, because cup letters above a D are labelled differently from one brand to the next. This guide covers how to measure, what the US cup sequence actually is, and how your size converts to UK and EU labels. Run your numbers through the calculator on the home page for all three at once.
Use it as a US bra size calculator in inches, a US to UK bra size calculator, or a US to Europe bra size converter. The result is a practical starting size for everyday and plus size fitting, not a promise that every brand will fit identically.
How to Measure Your US Bra Size
Two measurements, taken with a soft tape measure while wearing a thin, non-padded bra or none at all.
- Band: Measure snugly around your ribcage, directly under your bust. Keep the tape level and pull it firm. Round to the nearest whole inch.
- Bust: Measure loosely around the fullest part of your bust, tape parallel to the floor, without compressing.
- Cup: Subtract the band number from the bust number. Each inch of difference equals one cup size.
Don't add 4 inches. Many older American size charts still tell you to add 4 or 5 inches to your underbust measurement. That rule comes from an era before stretch fabrics, when the extra allowance was needed just to fasten the band. Today almost every bra contains spandex, and the addition produces a band that rides up and transfers the weight onto your shoulders. Our calculator uses your raw underbust measurement.
US Cup Size Chart
Where two letters appear below, both are in active use — the labelling depends on the brand, not on a different cup volume.
| Difference (inches) | Difference (cm) | US cup |
|---|---|---|
| 1" | 2.5 cm | A |
| 2" | 5 cm | B |
| 3" | 7.5 cm | C |
| 4" | 10 cm | D |
| 5" | 12.5 cm | DD or E |
| 6" | 15 cm | DDD or F |
| 7" | 18 cm | G (or DDDD) |
| 8" | 20 cm | H |
| 9" | 23 cm | I |
| 10" | 25 cm | J |
| 11" | 28 cm | K |
| 12" | 30 cm | L |
Why US Cup Labels Aren't Consistent
There is no single governing standard for American cup lettering above D. Some brands write DD, others write E for exactly the same cup. Above that, one label might read DDD while another reads F, and a few use DDDD where most now use G.
The practical consequence is that you cannot rely on the letter alone when switching brands. What stays constant is the difference between your bust and band measurements — 6 inches is 6 inches, whether the tag says DDD or F. Knowing your measurement in inches, rather than just your letter, is the reliable way to shop across brands.
US to UK Bra Size Conversion
Band numbers are the same in both systems, and cup letters match up to DD. Beyond that the UK uses a sequence of single and double letters that does not line up with American labelling.
| Difference | US cup | UK cup |
|---|---|---|
| 4" | D | D |
| 5" | DD | DD |
| 6" | DDD | E |
| 7" | G | F |
| 8" | H | FF |
| 9" | I | G |
| 10" | J | GG |
| 11" | K | H |
| 12" | L | HH |
A US 34DDD is a UK 34E, and a US 32H is a UK 32FF. British brands such as Panache, Freya and Bravissimo use the UK sequence, so check the letter carefully before ordering.
US to EU Bra Size Conversion
European band numbers are your underbust measurement in centimeters, rounded to the nearest 5 — which is why they look nothing like American ones.
| US band | Underbust (approx.) | EU band |
|---|---|---|
| 28 | 71 cm | 70 |
| 30 | 76 cm | 75 |
| 32 | 81 cm | 80 |
| 34 | 86 cm | 85 |
| 36 | 91 cm | 90 |
| 38 | 97 cm | 95 |
| 40 | 102 cm | 100 |
EU cup letters run in one continuous sequence with no doubled letters, so a US DD is an EU E and a US DDD is an EU F. Labelling varies slightly between European brands, so use the conversion as a starting point.
Sister Sizes
A sister size holds the same cup volume on a different band. If your calculated size is sold out or the band feels wrong, move one step in either direction: down a band and up a cup, or up a band and down a cup.
| Tighter band | Calculated size | Looser band |
|---|---|---|
| 32D | 34C | 36B |
| 34D | 36C | 38B |
| 32DDD | 34DD | 36D |
| 34G | 36DDD | 38DD |
Sister sizing changes how the bra sits, not how much it holds. If the cups fit but the band rides up, going down a band and up a cup usually solves it.
Plus Size Fitting
The same measurement method applies at every size. Two things matter more as the size increases: the band should be firm enough to carry the weight without help from the straps, and the cups need to contain tissue at the side as well as the front. Wider straps, deeper side panels and a three or four hook closure all improve comfort, and are worth prioritising over styling.
If you measure above a DDD, general-market retailers may not stock your size. Specialist fitters carry a considerably wider cup range.
Frequently Asked Questions
Is a DD the same as an E?
In American sizing, yes — both refer to a 5-inch difference. Some brands print DD, others print E. In UK sizing they are different cups: a UK DD is 5 inches and a UK E is 6 inches.
What comes after DDD?
Most US brands go to G next, then H, I, J. A few use DDDD instead of G. Because it varies, match on the inch difference rather than the letter.
My band measurement is an odd number. What do I do?
Round to the nearest even number, since US bands are sold in even sizes. If you're on the boundary, try the smaller band first — bands stretch with wear, and buying on the loosest hook leaves room to tighten later.
Why does my size differ between brands?
Cup depth and band tension are not standardised in the US. A 34D from two brands can fit noticeably differently. Your measurements stay constant, so use those as the reference and expect to adjust by a sister size depending on the brand.
Does this bra size calculator work for USA plus size?
Yes. The same band and bust measurement method works for plus size and full bust fitting. The calculator gives a starting size, then the fit should be checked for band support, cup coverage, side containment, and strap comfort.
Is this a US to UK bra size calculator?
Yes. The calculator gives both US and UK results, and the conversion chart explains where the two systems split after DD.
Can I convert a US bra size to Europe?
Yes. US bands convert to EU band numbers such as 34 to 85 and 36 to 90. EU cup labelling can vary by brand, so use the result as a starting point and check the retailer's own size chart.
How often should I re-measure?
About once a year, and after any significant weight change, pregnancy, or breastfeeding.