1. Measure your snug underbust
Wrap the tape directly under the bust, parallel to the floor, and pull it firm enough that it does not slide.
Most common mistake: measuring loosely because a band is supposed to feel comfortable.
Direct-fit calculator
Bra Size Calculator: Find Your Size in Inches and CM
Enter two measurements — get your band and cup size in inches or cm.
Your measurements stay in your browser — nothing is stored or submitted.
How to Measure Your Underbust and Full Bust
Accurate numbers come from a snug underbust and a level full-bust measurement taken without a thickly padded bra. Take each measurement standing naturally, then use the calculator as a starting point rather than forcing the tape to match an old label.
2. Measure your full bust
Measure around the fullest part of the bust with the tape level. Avoid a thickly padded or push-up bra while measuring.
Most common mistake: letting the tape angle upward at the back or compressing the fullest point.
3. Check the result in a bra
Start on the loosest hook and look for a level band, contained cups, and straps that feel supportive without carrying all the weight.
Most common mistake: changing the cup letter when the band is the part that is wrong.
Bra Size Chart
This chart combines bands 28–46 with cup letters AA–K; your calculated cell highlights after you run the calculator. A chart is a comparison tool, while comfort and containment decide whether that starting size works in a particular bra.
| Band | AA | A | B | C | D | DD | DDD/E | G | H |
|---|---|---|---|---|---|---|---|---|---|
| 28 | 28AA | 28A | 28B | 28C | 28D | 28DD | 28DDD/E | 28G | 28H |
| 30 | 30AA | 30A | 30B | 30C | 30D | 30DD | 30DDD/E | 30G | 30H |
| 32 | 32AA | 32A | 32B | 32C | 32D | 32DD | 32DDD/E | 32G | 32H |
| 34 | 34AA | 34A | 34B | 34C | 34D | 34DD | 34DDD/E | 34G | 34H |
| 36 | 36AA | 36A | 36B | 36C | 36D | 36DD | 36DDD/E | 36G | 36H |
| 38 | 38AA | 38A | 38B | 38C | 38D | 38DD | 38DDD/E | 38G | 38H |
| 40 | 40AA | 40A | 40B | 40C | 40D | 40DD | 40DDD/E | 40G | 40H |
Full 28–46 size matrix
| Band | AA | A | B | C | D | DD | DDD/E | G | H | I | J | K |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 28 | 28AA | 28A | 28B | 28C | 28D | 28DD | 28DDD/E | 28G | 28H | 28I | 28J | 28K |
| 30 | 30AA | 30A | 30B | 30C | 30D | 30DD | 30DDD/E | 30G | 30H | 30I | 30J | 30K |
| 32 | 32AA | 32A | 32B | 32C | 32D | 32DD | 32DDD/E | 32G | 32H | 32I | 32J | 32K |
| 34 | 34AA | 34A | 34B | 34C | 34D | 34DD | 34DDD/E | 34G | 34H | 34I | 34J | 34K |
| 36 | 36AA | 36A | 36B | 36C | 36D | 36DD | 36DDD/E | 36G | 36H | 36I | 36J | 36K |
| 38 | 38AA | 38A | 38B | 38C | 38D | 38DD | 38DDD/E | 38G | 38H | 38I | 38J | 38K |
| 40 | 40AA | 40A | 40B | 40C | 40D | 40DD | 40DDD/E | 40G | 40H | 40I | 40J | 40K |
| 42 | 42AA | 42A | 42B | 42C | 42D | 42DD | 42DDD/E | 42G | 42H | 42I | 42J | 42K |
| 44 | 44AA | 44A | 44B | 44C | 44D | 44DD | 44DDD/E | 44G | 44H | 44I | 44J | 44K |
| 46 | 46AA | 46A | 46B | 46C | 46D | 46DD | 46DDD/E | 46G | 46H | 46I | 46J | 46K |
Current calculated sizeFor a cup-only view, find just your cup size.
Why Brand Sizing Can Vary
Your measurement result is a consistent starting point, not a promise that every label will fit identically. Brands can vary in band stretch, wire width, cup depth, and cup-letter grading, so use fit signs to decide what to try next.
| What varies | How it can change fit | What to do |
|---|---|---|
| Band stretch | A 34 band can feel firmer or looser from one fabric and brand to another. | Begin on the loosest hook; use a sister size only when the band is clearly wrong. |
| Cup shape | Two C cups can have different depth, wire width, and top-edge height. | Change the bra cut before assuming every gap or wrinkle means a different cup letter. |
| Label sequence | US and UK lettering diverges beyond DD, and some brands skip sizes. | Check the stated sizing system and the brand chart before ordering. |
What Are Sister Sizes?
Sister sizes keep close cup volume while changing the band: go down one band and up one cup, or up one band and down one cup. They are useful when the cup feels right but the band is clearly too loose or too tight. They are not a substitute for changing cup shape when gaping or wire width is the real issue.
| Size | Band feel | Cup volume | When to try |
|---|---|---|---|
| 32D | Firmer | Close to 34C | A 34 band rides up or shifts support to the straps. |
| 34C | Baseline | Baseline | The band is level and comfortably firm. |
| 36B | Looser | Close to 34C | A 34 band is painfully tight, not merely new-bra snug. |
If you measure 34C, read the 34C fit guide for the next size or shape to test.
US, UK, EU and FR Sizes Compared
For a US 34C starting point, common conversions are UK 34C, EU 75C, FR/ES 90C, AU 12C, and JP 75C. These labels are useful references, but each brand’s wire width, cup depth, and band stretch can change fit.
| System | 34C conversion |
|---|---|
| US | 34C |
| UK | 34C |
| EU | 75C |
| FR/ES | 90C |
| AU | 12C |
| JP | 75C |
Bra Size Calculator FAQs
Measurement gives you a reliable starting point; fit tells you whether to change the band, cup, or shape next. These answers explain how the calculator relates to the bras you try on.
Measure your snug underbust and fullest bust, then enter both numbers in the calculator. BraScale rounds the underbust up to an even band and compares the full bust with that band to find the cup letter. Treat the result as a starting size, then check band tension and cup shape.
The band is the number, such as 34, and describes the bra’s underband length. The cup is the letter, such as C, and comes from the difference between your full bust and rounded band. A cup letter cannot describe volume by itself because it changes with the band.
Older charts, brand grading, stretched bands, and different cup shapes can all make a label differ from a fresh measurement. Your current bra may also be a sister size rather than the same size. Start with the calculated size, then use fit signs—level band, contained cups, and a comfortable center—to refine it.
34C and 36B are sister sizes with close cup volume but different band tension. A 36B has a longer, looser band and a cup one letter smaller to balance that change. Try 36B when a 34 band is genuinely too tight; try 32D when 34 rides up.
Check the brand’s size chart first, because some brands skip sizes or use different cup sequences. Then use sister sizing: move down one band and up one cup, or up one band and down one cup. Keep the cup volume similar while testing the band tension and the shape of the cup.
Use whichever unit your tape measure shows most clearly. The calculator converts centimeters before applying the same direct-fit rules, so the result should match. Enter your raw underbust measurement, not the number printed on an old bra label; EU band labels are not raw centimeter measurements.
Related Tools & Guides
Use the focused tool that matches the question you have after finding a starting size. Each guide returns to the same direct-fit measurement rules.