Find Your Perfect Bra Size
Use our free bra size calculators, bra measurement charts, and fit guides to find your band size, cup size, and sister sizes—whether you're shopping in-store or online from brands around the world.
Bra Size Calculators & Tools
Pick a calculator below to get started. Each tool walks you through the measurements and gives you a size you can use immediately.
Bra Measurement Charts at a Glance
Your bra size has two parts: the band size (a number based on your underbust measurement) and the cup size (a letter based on the difference between your bust and underbust measurements). The quick-reference tables below show the standard US/UK sizing conventions.
Band Size Chart (Underbust to Band Size)
| Underbust (in) | Underbust (cm) | Band Size (US/UK) |
|---|---|---|
| 26–27 | 66–69 | 28 |
| 28–29 | 71–74 | 30 |
| 30–31 | 76–79 | 32 |
| 32–33 | 81–84 | 34 |
| 34–35 | 86–89 | 36 |
| 36–37 | 91–94 | 38 |
| 38–39 | 97–99 | 40 |
| 40–41 | 102–104 | 42 |
| 42–43 | 107–109 | 44 |
| 44–45 | 112–114 | 46 |
Cup Size Chart (Difference to Cup Letter)
Subtract your underbust measurement from your bust measurement, then match the difference to the cup letter below.
| Difference (in) | Difference (cm) | US Cup | UK Cup |
|---|---|---|---|
| 0–1 | 0–2.5 | AA | AA |
| 1–2 | 2.5–5 | A | A |
| 2–3 | 5–7.6 | B | B |
| 3–4 | 7.6–10.2 | C | C |
| 4–5 | 10.2–12.7 | D | D |
| 5–6 | 12.7–15.2 | DD | DD |
| 6–7 | 15.2–17.8 | DDD | E |
| 7–8 | 17.8–20.3 | G | F |
| 8–9 | 20.3–22.9 | H | FF |
| 9–10 | 22.9–25.4 | I | G |
| 10–11 | 25.4–27.9 | J | GG |
| 11–12 | 27.9–30.5 | K | H |
See the complete bra measurement chart page → for international conversions, sister sizes, and more.
How to Measure for a Bra
Accurate measurements are the foundation of a good fit. Here's how to take them at home:
- Wear a comfortable, unpadded bra (or measure bare-chested if you're comfortable) so padding doesn't skew your results.
- Use a soft measuring tape that lies flat and isn't twisted.
- Underbust: Wrap the tape snugly around your ribcage, directly under your bust, parallel to the floor. Exhale naturally and read the measurement.
- Bust: Wrap the tape around the fullest part of your bust, usually at nipple level, keeping it parallel to the floor and not too tight.
- Double-check: Take each measurement twice to confirm consistency. Record both inches and centimeters if possible.
For step-by-step guidance with visuals, visit our How to Measure Bra Size guide.
Common Bra Sizing Questions
What's the difference between US and UK cup sizes?
US and UK band sizes are generally the same (in inches), but cup progressions diverge above DD. The US progression is typically AA, A, B, C, D, DD, DDD, G, H, I, J, K, while the UK progression is AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J. So a US 34DDD is roughly a UK 34E, and a US 34G is roughly a UK 34F. Always check the specific brand's chart when possible.
Why do EU sizes look so different?
EU band sizes use centimeters and add a standard 10 cm to the underbust measurement, while US/UK sizes use inches. That's why an EU 75 band corresponds roughly to a US/UK 34 band. Use a conversion chart rather than converting manually.
What are sister sizes?
Sister sizes have the same cup volume but different band sizes. Moving one band size up and one cup size down (or vice versa) gives you a close alternative—for example, 34C → 36B or 34C → 32D. They're useful when your exact size is unavailable or the band fit is slightly off. Try our Bra Sister Size Calculator to find yours.
How often should I re-check my bra size?
Every 6–12 months, or after significant body changes such as weight loss/gain, pregnancy, hormonal shifts, or changes in exercise habits. Bras also lose elasticity over time, so even unchanged measurements may call for a new size if your current bras feel loose or unsupportive.