Forget the measuring tape. Start by understanding how bra sizing works and what the right fit should feel like. Our guide gives you the tools you need to fit yourself. It’s easier than you think.

Bra Sizing

Many factors can affect your bra size such as pregnancy, hormones, weight fluctuations, exercise, etc. It’s important to re-evaluate your bra fit once a year.

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Evaluating Fit

There are 4 key areas that determine how well your bra fits. Instead of using a tape measure, our approach to bra fitting is to give you the knowledge you need to fit yourself.

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Troubleshooting Fit

Now that you’ve assessed the fit, here are some solutions to common bra fit problems.

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Sizing Charts

A summary of size conversions for bras, bodysuits, slips and knickers.

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Find your perfect fit

Bra sizes are made up of a number and a letter. The number represents your back size and the letter represents cup volume.

The letter (cup) does not represent one single size (i.e. not all B cups are the same size). The letter represents a difference (in inches) between the back and bust measurement.

One inch difference is an A, the second is a B, the third a C, the fourth a D, and so on.

Each column in our size chart below represents bras with the same cup size, but different back sizes. For example, 36A, 34B, 32C and 30D all have different back sizes, but share the same cup size. They are often referred to as ‘sister sizes’.

When changing bra sizes, always remember: If you change your back size, the cup size will also change.

For example: 34DD is a back size AND a cup size bigger than a 32DD

32A 34A 36A
30B 32B 34B 36B 38E 40B
30C 32C 34C 36C 38C 40C
30D 32D 34D 36D 38D 40D
30DD 32DD 34DD 36DD 38DD
30E 32E 34E 36E
30F 32F 34F
30G 32G

A = 1” difference

B = 2” difference

C = 3” difference

D = 4” difference

DD = 5” difference

E = 6” difference

F = 7” difference

G = 8” difference

Evaluating Fit

1. UNDERBAND

The underband/band is the anchor of your bra. It’s where most of the support will come from. Fasten your bra on the loosest hook and eye setting. This will allow you to tighten your bra (and keep it fitting perfectly) as it starts to ease out over time.

The band should fit snugly (you should only be able to fit two fingers under it) and lie parallel to the floor all the way around your body, even when you shrug your shoulders or move around.

2. STRAPS

Since the band is your bras main source of support, straps do not need to carry any weight or dig into your shoulders.

They should just be resting on your shoulders, with roughly 2” of slack when lifted off the body. It’s ok if one is shorter than the other as the left and right breast are often different sizes.

3. CUPS

Women often wear cups that are too small, causing breast tissue to spill out at the top or sides. If they’re too big the cup hangs away from the body. Aim for a smooth, snug fit.

4. CENTRE FRONT

The reinforced front part of the band that lies between the breasts. On underwired bras, the centre front should fit flat against your chest. If it’s lifting away, your cups might be too small.

On wireless bras, the centre will lift away slightly.

5. UNDERWIRE

Wires (or if you’re wearing a wireless bra - the seam connecting the cups to the underband) should lay flat against your rib cage, including under your arms.

Troubleshooting Fit

Now that you’ve assessed the fit, here are some solutions to common bra fit problems.

Bra Cups Puckering?

Lift yourself up and into each bra cup. Tighten the straps so you have about 2” of slack on each side when the straps are lifted off your shoulders. If your cup size is still too large, go down a cup size.

Example: You’re wearing a 34D and the cups are puckering, but the back fits perfectly. Try going down a cup size to 34C.

Bulging out of the top or sides of your bra cups?

Your cup size could be too small. Try going up a cup size or choose a bra style that offers more coverage for example, a Classic bra, Balconette or Longline instead of a Demi Cup. Browse Bras

Example: You’re wearing a 34D and the back fits perfectly, but you’re bulging out of the top/sides of the cups. Go up a cup size to 34DD.

One cup fits fine, but the other cup puckers?

This is very common as left and right breasts are often different sizes. You should always fit to the larger cup. Adjusting the straps or trying a style with a different fabric may help hide the difference.

Underwires tip away from your body at centre front? Your bra cups are too small. Try a larger cup size.

Example: You’re wearing a 34E and the back fits perfectly, but you’re bulging out of the top/sides of the cups. Go up a cup size to 34F.

Bra is riding up in the back?

Your band size is too large. Try going down a back size. The band should fit snugly enough that it lies parallel to the floor even after moving around and shrugging your shoulders.

Example: You’re wearing a 34E and the cups fit well but the band is too loose. Go up a cup size (to keep the same cup size) and down a back size to 32F.

Shoulder Straps dig into your shoulders?

If the straps are digging in or you’re feeling strain on your shoulders, it might be a sign that the under bust band is too big and not giving enough support.

Example: You’re wearing a 32E and the cups fit well but the straps are digging into your shoulders. Go up a cup size (to keep the same cup size) and down a back size to 30F.

If after being adjusted, the straps are slipping down your shoulders it might mean that your band size is too small. Try going up a band size and down a cup size to compensate.

Example: You’re wearing a 34E and the cups fit well but the straps are falling off your shoulders, go down a cup size (to keep the same cup size) and up

a back size to 36DD.

Back size too loose and cup too small?

Example: If you’re wearing a 34E and finding the cups and band are too big. Go down a back size to 32E.

The back size is too big and the cup size is too small?

Example: If you’re wearing a 34E go down a back size to 32, and up two cup sizes to G (32G).

Navigating Size Changes

How To Change Sizes Depending On Your Fitting Needs

The back size is too small, but the cup size fits perfectly

Go up a back size and down a cup size

The back size .fits perfectly, but the cup size is either too big or small

Keep the same back size, but go up or down a cup size accordingly

The back size and the cup size are both too small

Go up a back size

The back size and the cup size are too big

Go down a back size

The back size is too big and the cup size is too small

Go down a back size and up two cup sizes

The back is too small and the cups are too big

Go up a back size and down two cup sizes

Sizing Charts

A summary of size conversions for bras, bodysuits, slips and knickers.

International Bra Band Sizes

Fortnight North America UK Europe France Italy Australia Japan
30 30 30 65 80 0 6 65
32 32 32 70 85 1 8 70
34 34 34 75 90 2 10 75
36 36 36 80 95 3 12 80
38 38 38 85 100 4 14 85

International Cup Sizes

Fortnight North America UK Europe France Italy Australia Japan
A A A A A A A A
B B B B B B B B
C C C C C C C C
D D D D D D D D
DD DD or E DD E E E E E
E DDD or F E F F F F F
F G F G G F F G
G H FF H H FF FF I

Triangle Bra Sizes

Fortnight Bra Size
XS A 30/32. B 30
S B 32. C 30/32. D 30
M A 36. B 34. C 34. D 32/34. DD 30/32
L B 36. C 36

Bodysuit, slip & One-piece Swimwear sizes

Fortnight Bra Size Waist Hips
S (0-2) A32-34, B30-34, C30-32, D30 24-26 35-36
M (4-6) B34, C34-36, D34-34, DD30-32, E30 27-28 37-38
L (8-10) D34-36, DD 32-34, E30-32, F30 29-30 39-40
XL (10-12) DD36, E32-34, F 32-34, G 32 31-32 41-42

Please Note: Bodysuit sizing is tricky as you're combining 3 different proportions (bust, bottom and torso) into one. Please don't hesitate to contact us with questions, we're happy to help!

Lingerie & Swim Bottom Sizes

Fortnight Waist Hips
S (0-2) 24-26 35-36
M (4-6) 27-28 37-38
L (8-10) 29-30 39-40
XL (10-12) 31-32 41-42
XXL (12-14) 33-34 43-44

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