Bra Size Chart: US Bands, Cups and Sister Sizes
Use the US bra size chart alongside the calculator. Measure a snug underbust and the fullest standing bust in the same unit, choose a band method, then compare the calculated cup step with the chart. International labels and sister sizes are reference starting points; brand charts and actual fit can differ.
- Free to use
- No sign-up
- Runs in your browser
Bra size calculator
Keep the tape level. Enter your measured values in inches or centimetres without first rounding them. The modern method rounds underbust to the nearest even inch; the traditional method rounds to an inch and adds 4 to an even value or 5 to an odd value. Cup steps are rounded from bust minus the calculated band.
This calculator limits US bands to 28–48 and cup steps to 0–12 (AA–L in its US labels). Values outside those ranges are capped, so an extreme input is not evidence that the displayed size fits.
Bra Fit Guide Pack
Printable bra size charts (US, UK, EU, FR, AU), a sister size chart, a measuring guide, a bra fit checklist and a bra wardrobe log (Excel).
- Cup conversion (PDF/XLSX)
- Band conversion (PDF)
- Sister sizes (PDF)
- Fit checklist (PDF, DOCX)
- Wardrobe log (XLSX)
Formats: PDF, XLSX, DOCX. Instant download after payment (link valid 72 hours, up to 5 downloads). AI-assisted: the templates were drafted with AI help and reviewed and laid out before publishing.
$3.00 USD, one-time 5 files · about $0.60 each
- Instant download
- 7-day refund
- Secure checkout by Stripe
7-day money-back guarantee. Full refund within 7 days of purchase, even after you download.
Free sample: Bra Band Conversion (PDF, 60 KB)
Full refund within 7 days — see the refund policy and license.
Free printables
Single sheets you can print right now, no sign-up. The full pack adds every sheet in one download plus the editable files.
Bra Fit Checklist Printable
Printable Bra Wardrobe LogHow bra sizes work
A bra size has two parts. The band size (32, 34, 36…) relates to the measurement around your ribcage under the bust. The cup letter shows the difference between the bust measurement and the band: each inch of difference is one cup size. A 34C means a 34-inch band with a bust about 3 inches larger (37 inches). Because cup volume depends on the band, a C cup on a 38 band holds more than a C cup on a 30 band.
US cup size chart
| Bust − band (in) | US cup | UK cup | EU cup |
|---|---|---|---|
| 0 | AA | AA | AA |
| 1 | A | A | A |
| 2 | B | B | B |
| 3 | C | C | C |
| 4 | D | D | D |
| 5 | DD / E | DD | E |
| 6 | DDD / F | E | F |
| 7 | G | F | G |
| 8 | H | FF | H |
| 9 | I | G | I |
| 10 | J | GG | J |
US brands differ in how they name cups above D: some use DD then DDD, others DD then E and F. UK sizing adds double letters (DD, FF, GG, HH), so a UK F is not the same as a US F. Always check which system a brand uses.
Measuring for a bra
- Wear a non-padded, well-fitting bra (or none).
- Underbust: wrap the tape snugly around your ribcage directly under the bust, level all the way round, and exhale. Enter the measured value; let the selected calculator method do the rounding.
- Bust: stand straight and measure loosely around the fullest part of the bust, tape level across the back.
- Some fitters also measure while leaning forward (bust hanging) and take the larger number for fuller or softer tissue.
- Enter the numbers in the calculator.
Modern and traditional band methods
The methods can produce different bands and cup letters from the same measurements. For an underbust of 31 inches and bust of 36 inches, this tool’s modern method gives 32D and its traditional method gives 36AA. Compare either starting point with the sizing guide for the bra you are trying.
Sister sizes and cup labels
Changing one band step and one cup step in the opposite direction gives a reference sister size: 34C corresponds to 32D or 36B in this chart. Similar cup volume does not guarantee the same fit across styles. See the sister sizes reference and cup conversion reference.
How a bra should fit
- Band — level all the way round and snug on the loosest hook; you should fit about two fingers under it.
- Cups — smooth with no gaping or spilling over the top or sides.
- Centre gore — the middle panel sits flat against the breastbone in underwired bras.
- Underwire — encloses breast tissue without sitting on it.
- Straps — stay in place without digging in; they should carry only a small part of the support.
Troubleshooting fit
| Problem | Likely fix |
|---|---|
| Band rides up at the back | Band too big — go down a band (and up a cup) |
| Straps dig in | Band too loose or straps too tight |
| Cups gape | Cup too big or wrong style for your shape |
| Spilling over cups | Cup too small — go up a cup |
| Centre gore lifts away | Cups too small or too shallow |
| Wires poke under arms | Try a different shape or smaller cup width |
International labels in this calculator
The chart and calculator use the same cup sequence. US 34DDD/F maps to UK 34E and EU 75F here. US 34C maps to UK 34C, EU 75C, French 90C and Australian 12C. These are reference labels; they are not a universal sizing rule for every brand.
When to re-measure
Measure again every six months or so, and after weight changes, pregnancy, breastfeeding, starting new exercise routines or hormonal changes. Bras also stretch with wear: a bra that fit on the loosest hook when new should still fit on the tightest hook later.
Privacy
Measurements are processed in your browser and never stored.
Frequently asked questions
How do I calculate my bra size?
Measure underbust (band) and bust; the difference in inches gives the cup — each inch is one cup size.
What does 34C mean?
A 34-inch band with about a 3-inch difference between bust and band.
What is a sister size?
A size with the same cup volume on a different band, such as 34C and 32D.
Is a US DDD the same as UK F?
No — a US DDD is roughly a UK E; UK uses double letters differently.
Should I add 4 inches to my band?
This calculator offers both methods. Modern rounds underbust to the nearest even inch; traditional rounds to an inch, then adds 4 for an even value or 5 for an odd value. Compare the result with your brand’s sizing guide and fit.
How often should I re-measure?
Every six months or after body changes.
What is the most common bra size?
There is no reliable single answer; sizes vary widely, and many people wear the wrong size, so measuring matters more than averages.
Do sports bras use the same sizes?
Many use band and cup sizes, others S–XL; check the brand chart and prioritise a firm band.
Why does my band ride up?
The band is probably too loose; try a smaller band with a larger cup (a sister size).
Is my data stored?
No, it runs in your browser.
Do the international sizes guarantee a fit?
No. This calculator uses fixed band and cup mappings. Brands may use different labels or grading, especially above D; compare their own chart before choosing a size.
Can I measure in centimetres?
Yes. Choose cm for both measurements. The calculator converts them using 2.54 centimetres per inch before applying the selected band method.