Maternity & Nursing Bra Size Guide: How to Measure for the Correct Fit
Your bra size changes during pregnancy and breastfeeding. Most women go up 1-2 band sizes and 2-3 cup sizes. Getting your maternity bra size right from the start saves money and prevents discomfort from ill-fitting bras.
This guide shows you how to measure for maternity and nursing bras in 3 simple steps. Use our free size calculator to find your correct fit, then check the Australian size chart for your band and cup measurements.
Once you know your size, check our best nursing bras Australia guide to find the right style.
How Much Does Bra Size Increase During Pregnancy?
Your breasts start changing in the first trimester. Hormones trigger milk duct development and increased blood flow. Most women notice tenderness and fullness within the first 6-8 weeks.
Typical bra size changes:
• Band size: Increases 1-2 sizes as ribcage expands
• Cup size: Increases 2-3 sizes during pregnancy
• Postpartum: Additional 1 cup size when milk comes in (temporary)
A woman who starts pregnancy as 12C (34C) might measure 14E (36DD) by her third trimester. This is why measuring at key points matters. Buying bras too early means they won't fit later.
Your ribcage expands during pregnancy to accommodate your growing baby, which is why band size increases alongside cup size.
Your ribcage returns to pre-pregnancy size within 6-8 weeks postpartum. Cup size depends on breastfeeding. Expect fluctuations until milk supply stabilises around 6-8 weeks after birth.
Wire-free bras are recommended during breastfeeding to reduce pressure on milk ducts and lower mastitis risk.
How to Measure Your Maternity & Nursing Bra Size
You need 2 measurements: band size and bust size.
What you'll need:
- Soft measuring tape
- Large mirror
- No bra or unpadded bra
- 5 minutes of your time
Step 1:
Measure Your Band Size
Stand straight. Wrap tape around your ribcage directly under your breasts.
Keep tape level and snug but not tight. Breathe normally. Measure on exhale. Round to nearest whole number.
Example:
- 81 cm (32 inches) = Band size 32
- 84 cm (33 inches) = Band size 34
Band size conversions:
- 10 = 81 cm (32 inches)
- 12 = 86 cm (34 inches)
- 14 = 91 cm (36 inches)
- 16 = 97 cm (38 inches)
- 18 = 102 cm (40 inches)
Step 2:
Measure Your Bust Size
Stand straight. Wrap tape around the fullest part of your breasts.
Keep tape level. Don't pull tight or compress breasts. Round to nearest whole number.
Example: 94 cm (37 inches) = Bust measurement
Cup size chart:
| Difference | Cup Size |
|---|---|
| 2.5 cm (1 inch) | A |
| 5 cm (2 inches) | B |
| 7.5 cm (3 inches) | C |
| 10 cm (4 inches) | D |
| 12.5 cm (5 inches) | DD/E |
| 15 cm (6 inches) | F |
| 18 cm (7 inches) | G |
| 20 cm (8 inches) | H |
Calculate Your Cup Size
Subtract band size from bust size. The difference = your cup size.
Example calculation:
- Bust: 94 cm (37 inches)
- Band: 81 cm (32 inches)
- Difference: 13 cm (5 inches) = DD cup
- Your size: 32DD (Australian 10DD)
Maternity Bra Fitting Tips
Best time: Morning before breasts swell.
Stand straight: Don't slouch. Affects ribcage measurement.
Breathe normally: Measure on exhale, not deep breath.
Measure twice: Confirm accuracy. Take average if different.
Get help: Partner ensures tape is level.
Write it down: Track measurements over time.
-
Maternity & Nursing Bra Size Calculator
Use this formula:
- Measure band (under breasts): _____ cm
- Measure bust (fullest part): _____ cm
- Calculate difference: bust - band = _____ cm
- Find cup size in chart above
- Your size = Band + Cup
Example:
- Band: 86 cm (34 inches)
- Bust: 99 cm (39 inches)
- Difference: 13 cm (5 inches) = DD
- Size: 34DD (12DD)
-
When to Measure: Pregnancy Bra Size Timeline
Your size changes throughout pregnancy. Measure at these key points:
- 16 weeks (4 months): First measurement. Most breast changes happen by 16 weeks. Buy 2-3 maternity bras.
- 32 weeks (8 months): Second measurement. Buy nursing bras for postpartum.
- 2 weeks postpartum: Final measurement after milk comes in and stabilises.
- Every 6-8 weeks: Check fit if bra feels uncomfortable.
Australian Maternity Bra Size Chart S, M, L, XL
| US/EU | A | B | C | D | E | F | G | H | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AU | EU | US | UK | A | B | C | D | DD | E | F | FF | |
| 10 | 70 | 32 | 32 | S | S | S | S | S | M | M | ||
| 12 | 75 | 34 | 34 | S | S | M | M | M | M | L | ||
| 14 | 80 | 36 | 36 | M | M | M | L | L | L | L | ||
| 16 | 85 | 38 | 38 | M | L | L | L | L | XL | XL | ||
| 18 | 90 | 40 | 40 | L | L | XL | XL | XL | XL | |||
| 20 | 95 | 42 | 42 | XL | XL | XL | XL | XL | ||||
| 22 | 100 | 44 | 44 |
How to use this chart:
- Find your band size (AU, EU, US, or UK)
- Find your cup size in the header row
- Follow down to find your bra size (S, M, L, XL)
Brand Size Guides: Cake Maternity, Hot Milk, Panache
Each maternity bra brand sizes differently. Use your measurements from the calculator above, then check brand-specific guidance.
Cake Maternity Size Guide
Cake Maternity uses Australian sizing. Their bras run true to size with consistent band measurements. If you measure 12DD, order 12DD.
• Band fit: True to size
• Cup fit: True to size
• Size range: 8-18 bands, B-J cups
• Best for: All bust sizes, consistent sizing across styles
→ Shop Cake Maternity bras
Hot Milk Lingerie Size Guide
Hot Milk Lingerie uses New Zealand/Australian sizing. Their bands run slightly generous. If you're between sizes, choose the smaller band.
• Band fit: Runs 1 size large (generous fit)
• Cup fit: True to size
• Size range: 8-24 bands, A-J cups
• Best for: Flexiwire styles, fashion-forward designs
Hot Milk also offers S/M/L/XL sizing for some styles. Use the size chart above to convert your cup-sized measurements. Hot Milk is known for flexiwire nursing bras that provide lift without rigid underwire.
→ Shop Hot Milk Lingerie bras
Panache Nursing Bra Size Guide
Panache uses UK sizing with firm band construction. Convert your Australian size to UK, and expect a snug band fit.
• Band fit: Firm (true UK sizing)
• Cup fit: True to size
• Size range: 8-20 bands, D-K cups
• Best for: Larger busts (D+ cups), maximum support
AU to UK band conversion: AU 10 = UK 32, AU 12 = UK 34, AU 14 = UK 36, AU 16 = UK 38
→ Shop Panache nursing bras
Shop Maternity Bras at Mumgerie
Find your correct bras size at Mumgerie. Australian sizes A-J cups, bands 8-24.
Why shop with us:
- Expert fitting advice
- Free shipping over $150
- Express delivery options
- Curated products by mums
Get maternity bra sizing right. Your body deserves proper support.
Shop now:
Frequently Asked Questions
Re-measure every 6-8 weeks. Your ribcage expands and breast tissue grows throughout pregnancy. Your body changes significantly at different stages.
Key measurement points: 16 weeks, 32 weeks, 2 weeks postpartum.
Choose the larger size. Bras stretch with wear. You can tighten the band using hooks. You can't make a too-small bra bigger.
If between band sizes, try the smaller band with larger cup (same volume). Example: Between 34C and 36C? Try 34D.
No. Buy nursing bras that fit at 32-36 weeks. Your breasts are already close to breastfeeding size.
Expect temporary 1 cup size increase when milk comes in (days 2-5). According to Raising Children Network, breast engorgement settles within 2 weeks as
feeding establishes. Buy sleep nursing bras 1 size larger for overnight engorgement only.
Band: Sits level around body. Doesn't ride up back. You can fit 2 fingers under band. Feels snug on loosest hook.
Cups: Breast fills cup completely. No overflow at top or sides. No gaps or wrinkles. Nipple points forward.
Straps: Stay on shoulders. Don't dig in. You can fit 2 fingers under strap.
If band rides up, you need smaller band size. If breast spills over, you need larger cup size.
A poorly fitting bra can contribute to blocked milk ducts, so getting the right fit matters for breast health.
Usually no. Both wire-free and flexiwire styles use the same size. The difference is support structure, not sizing.
Wire-free nursing bras have stretchy fabric and no rigid support. They accommodate size fluctuations well. Choose your measured size.
Flexiwire nursing bras have flexible underwire that moves with your body. They provide more lift and shape. Choose your measured size. If between sizes, the larger size may feel more comfortable as flexiwire has less stretch than wire-free styles.
32-36 weeks is ideal. Most breast growth is complete. You're close to final breastfeeding size.
Professional fitting helps if:
- First time buying maternity bras
- Larger bust (D+ cups)
- Unsure about size between brands
- Want expert advice on styles
DIY measuring at home works well for tracking changes and online shopping.
No. Brands size differently:
Cake Maternity (Australian) runs true to size. Consistent band sizing.
Hot Milk Lingerie (New Zealand) runs slightly generous. Band may run large by 1 size.
Panache Nursking Bras (UK) runs true to UK sizing. Firm band. Best for larger busts.
Always check brand-specific size charts. When between sizes, choose larger size.
Buy nursing bras at 32-36 weeks pregnant. Your breasts are close to breastfeeding size by then.
Measure yourself using the steps above. Buy bras that fit on the loosest hook setting. This gives room to tighten as your ribcage returns to pre-pregnancy size after birth.
Expect your cup size to increase 1 size temporarily when milk comes in (days 2-5 postpartum). This settles within 2 weeks. Don't buy all your nursing bras in a larger size based on engorgement. Buy 1-2 sleep bras in a larger size for overnight fullness.
Use the same measurement method as maternity bras. Measure your band (under bust) and bust (fullest part). Calculate the difference to find your cup size.
Nursing bras and maternity bras use the same sizing. The difference is the nursing clips for feeding access. Any bra size you calculate works for both maternity and nursing styles.
If you already know your maternity bra size, use the same size for nursing bras. Re-measure at 2 weeks postpartum once milk supply stabilises if bras feel uncomfortable.
Sister sizing means adjusting band and cup together to maintain the same cup volume. When you go up a band size, go down a cup size. When you go down a band size, go up a cup size.
Example: 12D, 14C, and 10DD are sister sizes. They have the same cup volume but different band fits.
Sister sizing helps when:
• Band fits but cups are slightly off
• Your usual size is unavailable
• A specific style runs large or small in the band
If your 12D feels tight in the band but cups fit well, try 14C. Same cup volume, roomier band.