Enter your measurements and discover your ideal fit across every international sizing system in seconds.
The Snug method uses a tighter underbust measurement. Popular with UK fitters, no +4/+5 addition needed.
The Loose method takes a relaxed underbust and adds inches to determine band size. Traditional US/AU department store approach.
The Bra Fitter Pro uses all three measurements, snug underbust, loose underbust and full bust, for the most accurate recommendation.
Getting your size is simple. Follow these steps for the most accurate result using any of our four calculation methods.
Use a flexible dressmaker's tape. Avoid stretchy or rigid tapes, they give inaccurate results. Stand straight, breathe normally.
Wrap the tape directly below your bust, against your skin. Keep it level and parallel to the floor.
Wrap the tape around the fullest part of your bust. Keep it snug but not tight, a good fit leaves room to breathe.
Input your measurements in inches or cm, choose your preferred sizing system, and hit Calculate.
Your results include sister sizes, alternative bands and cups that give the same cup volume for more shopping flexibility.
Use your calculated size as a starting point. Fit can vary by brand. Adjust by one size if the band feels too tight or loose.
Precision matters. Small errors in measurement can mean one or two sizes off. Here's exactly how to measure each area.
Stand straight and exhale naturally. Wrap the tape measure snugly around your torso directly underneath your breasts, where a bra band would sit. The tape should be level all the way around, check in a mirror. Round to the nearest inch or half-centimetre.
Lean forward slightly at a 90° angle so your breast tissue falls naturally forward. Wrap the tape around the fullest part of your bust. The tape should be parallel to the floor and just touching the skin, not pulling it. This lean-forward method is used by professional fitters worldwide.
For the Snug Method, pull the tape measure fairly firmly, tighter than normal comfort, but not enough to cause pain or visible marks. This removes the need for the traditional "+4 inches" calculation and gives a more precise modern band size.
For the Loose Method, let the tape rest comfortably around your ribcage with minimal tension, you should easily slip 2–3 fingers underneath. This measurement is used in the traditional +4/+5 formula still used by many department stores and older sizing guides.
Sizes vary significantly between countries. Use this chart to convert your size when shopping internationally.
| US / Canada | UK / AU / NZ | EU | FR / ES / BE | IT | JP |
|---|---|---|---|---|---|
| 30 | 30 | 65 | 80 | 0 | 65 |
| 32 | 32 | 70 | 85 | 1 | 70 |
| 34 | 34 | 75 | 90 | 2 | 75 |
| 36 | 36 | 80 | 95 | 3 | 80 |
| 38 | 38 | 85 | 100 | 4 | 85 |
| 40 | 40 | 90 | 105 | 5 | 90 |
| 42 | 42 | 95 | 110 | 6 | 95 |
| 44 | 44 | 100 | 115 | 7 | 100 |
| Cup Diff (in) | US / UK Cup | EU / FR Cup | IT Cup | Description |
|---|---|---|---|---|
| 0" | AA | AA | AA | Very small cup volume |
| 1" | A | A | A | Shallow projection |
| 2" | B | B | B | Average volume |
| 3" | C | C | C | Moderate full |
| 4" | D | D | D | Fuller cup |
| 5" | DD / E | E | DD | Full cup |
| 6" | DDD / F | F | E | Very full |
| 7" | G | G | F | Extended sizing |
| 8" | H | H | G | Extended sizing |
| 9" | I | I | H | Plus sizing |
| 10" | J | J | I | Plus sizing |
Getting the size right is just the beginning. These tips from professional bra fitters will help you find true comfort.
A new bra should fit comfortably on the loosest hook. As the bra stretches over time, you move to tighter hooks to maintain support.
Slide two fingers under your band. If it's too easy, the band is too loose. If you can't fit them in, it's too tight.
Lean forward and gently scoop all breast tissue into the cup. This ensures all tissue is contained and the bra sits correctly.
The centre panel should lie flat against your sternum. If it's floating, try a larger cup. If it digs in, try a smaller cup.
Only 10–20% of support should come from straps. The band provides 80%. If straps dig in, try tightening your band instead.
Can't find your exact size? Sister sizes have the same cup volume: e.g., 34C = 32D = 36B in terms of cup fullness.
Weight changes, hormones, pregnancy and ageing all affect your bra size. Re-measure annually or whenever your clothes fit differently.
Sizes aren't universal across brands. When trying a new brand, try your calculated size plus one size up and one down.
Everything you need to know about bra sizing, measurement methods, and fit.
We believe every woman deserves a bra that fits, and that finding your size should be simple, free, and accurate.
Brasy was built out of frustration with the outdated +4 sizing method that leaves millions of women wearing the wrong size bra. Research suggests up to 80% of women are wearing incorrectly fitted bras, leading to back pain, shoulder strain, and chronic discomfort.
Our calculator incorporates four different measurement methods, Standard, Snug, Loose, and the Professional Fitter approach, to give you the most comprehensive result possible. We support all major international sizing systems so you can shop confidently anywhere in the world.
Every formula on Brasy has been reviewed against guidelines from professional lingerie fitters and bra-fit communities. We update our calculations as industry standards evolve.