How to Measure Your Bra Size at Home (Australian Sizes)
Measure your bra size at home in five minutes with a soft tape, work out your Australian band and cup size, and check the fit, from a lingerie brand founder.
The short answer
You need two measurements: your underbust (around your ribcage, just under your bust) and your bust (around the fullest part). Your underbust gives your band size; the difference between the two gives your cup size. Then check the fit on your body, because the right bra is the one that fits, not the one the tape suggests.
As the founder of the TOZAHIDA lingerie brand and a textile engineer, I see the same sizing mistakes again and again. Most of them come from a band that is too big and a cup that is too small. Here is how to get it right.
What you need
- A soft tape measure (a sewing tape, not a metal one)
- A mirror
- An unpadded bra, or no bra
- Five minutes
Step 1: Measure your underbust
Wrap the tape around your ribcage directly under your bust. Keep it level all the way around, and snug but not digging in. Breathe out normally and read the measurement in centimetres.
Step 2: Measure your bust
Measure around the fullest part of your bust, usually across the nipples, keeping the tape level and loose enough not to compress the breast tissue. Leaning forward slightly can help if you have a softer or fuller bust.
Step 3: Work out your size
Band: match your underbust to the band size.
| Underbust (cm) | AU band | US / UK |
|---|---|---|
| 63–67 | 8 | 30 |
| 68–72 | 10 | 32 |
| 73–77 | 12 | 34 |
| 78–82 | 14 | 36 |
| 83–87 | 16 | 38 |
| 88–92 | 18 | 40 |
Cup: subtract your underbust from your bust. Each cup is roughly 2 cm.
| Difference (cm) | 10–12 | 12–14 | 14–16 | 16–18 | 18–20 | 20–22 |
|---|---|---|---|---|---|---|
| AU cup | A | B | C | D | DD | E |
Example: underbust 75 cm and bust 91 cm gives a difference of 16 cm, so a 12C or 12D. Try both. Our full Size Guide has the complete charts, including clothing sizes.
Step 4: Check the fit
- Band: level all the way around, firm on the loosest hook when new. You should fit two fingers under it, not more. The band does about 80% of the support.
- Cups: no gaping at the top and no spilling over the edge or sides.
- Centre front (gore): on an underwire bra it should sit flat against your breastbone.
- Underwire: sits behind the breast tissue at the sides, not on it.
- Straps: stay put without digging in. If you need to tighten them a lot, the band is probably too loose.
Sister sizes
If the cups fit but the band is too loose, go down a band and up a cup (12C to 10D). If the band is too tight, go up a band and down a cup (12C to 14B). These “sister sizes” hold about the same cup volume.
- Unlined, seamless cups
- 76% polyamide, 24% spandex
- Over 1,600 ratings
Best smooth everyday fit
Check price on Amazon AU Price & availability shown on Amazon.com.auWacoal Basic Beauty Spacer T-Shirt Bra (Plus Size)
- Spacer foam cups
- Underwire
- Over 5,000 ratings
Best for fuller busts
Check price on Amazon AU Price & availability shown on Amazon.com.auFrequently asked questions
How often should I measure my bra size?
Every 6–12 months, and after weight changes, pregnancy or starting new exercise. Your size can change more often than you think.
Why does my bra size differ between brands?
Bras are made on different patterns, cup shapes and fabrics. Stretchy lace fits differently from moulded foam. Use your measured size as a starting point, then go by fit.
Should I go up a band size for comfort?
Usually no. A loose band rides up and puts the weight on your shoulders. Try a sister size instead.
What type of bra suits my shape?
See our guide to types of bras explained.