Find Your Perfect Bra Size
Enter your band and bust measurement to get your exact US, UK, EU, and AUS sizing. Round-trip everything in inches or centimeters — no guesswork, no sign-up.
🎀 Bra Size Calculator
Your Estimated Size
32D
Band Size
32
Cup Difference
4"
MEASURING TIPS
How to Measure Correctly
Accurate measurements are everything. Follow these three steps for the best fit.
Use a soft tape measure
A flexible tape measure gives an accurate reading — a rigid ruler or dressmaker's stick won't wrap the body correctly.
Measure without a bra
Take both measurements against bare skin or a thin, non-padded top so the tape sits flush against your body.
Breathe naturally
Keep the tape snug but not squeezing, and breathe out normally before reading the number — don't suck in or hold your breath.
The +4 Rule (Sister Sizing)
If your band measurement lands on an odd number (say 31"), round up to get an even band size. Your calculated size is your "sister size" — moving one band size up and one cup size down (or one band size down and one cup size up) keeps roughly the same cup volume while changing how the band fits. If a 34C feels tight in the band, try its sister size, 36B, for a looser band with the same cup comfort.
INTERNATIONAL SIZING
International Size Chart
| US Band | UK Band | EU Band | AUS Band |
|---|---|---|---|
| 28 | 28 | 90 | 28 |
| 30 | 30 | 92 | 30 |
| 32 | 32 | 94 | 32 |
| 34 | 34 | 96 | 34 |
| 36 | 36 | 98 | 36 |
| 38 | 38 | 100 | 38 |
| 40 | 40 | 102 | 40 |
| 42 | 42 | 104 | 42 |
| 44 | 44 | 106 | 44 |
Cup Letter Conversion
| US / UK Cup | EU Cup | AUS Cup |
|---|---|---|
| AA / AA | AA | AA |
| A / A | A | A |
| B / B | B | B |
| C / C | C | C |
| D / D | D | D |
| DD / E | E | E |
| DDD / F | F | F |
| G / FF | FF | FF |
| H / G | G | G |
This chart is a general sizing guide built from one consistent conversion table — it is not a medical, legal, or brand-certified standard. Individual manufacturers vary.
Signs Your Bra Doesn't Fit
- Band rides up: the back band should stay level and parallel to the floor, not creep upward.
- Straps dig in: straps digging into your shoulders usually mean the band is doing too little work.
- Cup overflow or gaps: overflowing cups mean size up a cup; gaping means size down.
- Centre gore doesn't sit flat: the underwire centre should rest flush against your breastbone.
Sister Sizing Explained
Sister sizes share the same cup volume but sit on different bands. Moving up a band size and down a cup size (or the reverse) keeps roughly the same cup volume with a looser or snugger band.
Bra Size Calculator — Find Your Perfect Fit
Finding the right bra size can be surprisingly difficult. Studies suggest that up to 80% of women wear the wrong size — either too tight in the band, too small in the cup, or both. It's a problem that provokes support issues, discomfort, and significantly worse posture and confidence.
Our free size calculator solves two of the most common problems at once: your band-to-bust circumference difference and international sizing chart differences. Because US, UK, EU, and Australian systems all label the same cup volume differently, converting between systems by hand is where most shoppers go wrong.
Use the calculator above, then read the sections below to understand exactly what the results mean, how to ensure fit, and how to shop with confidence.
How Bra Sizes Are Calculated
Bra sizing has two components: the band size (a number) and the cup size (a letter). The band number represents your ribcage circumference in inches, rounded up. The cup letter represents the difference between your bust and band measurement.
The Cup Size Formula
Cup Size = Bust Measurement (in) − Band Size (in)
0" difference = AA
1" difference = A
2" difference = B
3" difference = C
4" difference = D
5" difference = DD / E
6" difference = DDD / F
7" difference = G
8" difference = HBand Size Rounding Rule
Band sizes round to the nearest even number. If your unrounded band measurement is odd (say 33"), you round up to the nearest even number (34"). Both US and UK band sizes use this same rounding method, which is why band numbers are almost always even.
Bra Size Converter
Convert between US, UK, EU, and Australian sizing systems in one place.
Step-by-Step Measurement Guide
Step 1 — Measure Your Band
Wrap a soft tape measure snugly around your ribcage, directly beneath your bust. The tape should sit level all the way around and rest firmly against your ribs — not so tight it digs in, not so loose it slips down. Read the measurement to the nearest whole inch or centimeter.
Step 2 — Measure Your Bust
With either a bare chest or a thin, unpadded top, wrap the tape around the fullest part of your bust — usually across the nipple line — keeping it level with the floor front to back. Don't pull the tape tight; it should sit flush against your skin without compressing tissue.
Step 3 — Calculate the Difference
Subtract your band measurement from your bust measurement. The result maps directly to your cup letter using the formula above. Enter both measurements into the calculator and it will do this math for you automatically.
Tips for the Most Accurate Result
Measure while wearing a bra that fits reasonably well but isn't heavily padded — this keeps your natural shape without flattening or exaggerating it. If your numbers seem off, measure twice and use the average, and always weight the fit-check against the shape of your ribs before pulling too tight.
Understanding International Bra Sizing Systems
US & UK Sizing
US and UK sizes use the same band numbers (in inches, e.g. 32, 34, 36) and largely the same cup letters up to D. Where sizing traditionally diverges is above D: US labeling often uses DD and DDD, while UK labeling uses E, F, FF, and G for the equivalent cup volumes, which is where most cross-shopping confusion happens.
EU Sizing
European band sizing is centimeter-based in increments of 5 (60, 65, 70, 75, 80...). An EU band roughly equals your US/UK band converted to centimeters and rounded to the nearest EU step, and EU cup letters generally track US/UK letters one-for-one, but always confirm against the size chart above rather than assuming.
Australian Sizing
Australian and New Zealand band sizes run about 20 numbers lower than the equivalent US/UK band — a US 34 is roughly an AUS 14. Australian cup letters can also shift by one step at the higher end of the range, so use the converter above when shopping AUS/NZ brands rather than matching numbers directly.
Tips for Getting the Perfect Bra Fit
The Wire/Support Role
About 80% of your support should come from the band, not the straps. Straps that dig in and leave marks usually mean it's time to size down the band or loosen a hook while going up cup volume to keep the same fit.
Cup Fit Checkpoints
The cup should fully encapsulate the breast with no spillage over the top or sides (overflow), and no gaping or wrinkling in the fabric (underfill). If either shows up at the strap you should usually adjust cup size, not band size.
When to Size Up or Down
If the band feels tight the cup is too small, if the cup is too small, size up a cup — or use a sister size. If a bra feels loose right out of the box, size down the band and go up one cup using the same sister-size logic.
Wearing on the Loosest Hook
New bras should sit comfortably on the loosest hook so you have room to tighten as the band stretches over time with wear and washing — moving to the middle and then the tightest hook extends its usable life significantly.
— FAQ