18A Bra Size – Find Your Perfect Fit
What is 18A? Understanding the Band and Cup Size
In Australian sizing, an 18A bra means your band size is 18 and your cup size is A. This size is ideal for those with a larger body size but a smaller bust measurement. The number "18" refers to the underbust measurement – the area directly beneath your breasts – and typically corresponds to approximately 93–97 cm (36.5–38 inches). The "A" cup represents a smaller bust volume. It’s a unique combination that requires a thoughtfully designed bra to offer both comfort and support.
International Size Equivalents for 18A
| Region | Equivalent Size |
|---|---|
| Australia (AU) | 18A |
| UK | 40A |
| US | 40A |
| EU | 90A |
| France (FR) | 105A |
Use our complete size chart to compare and confirm your best fit.
How to Measure Your Bra Size with a Tape Measure
Not sure if 18A is your perfect match? Here’s a simple fitting guide using a tape measure:
- Step 1: Measure Your Band Size
Wrap the tape snugly around your ribcage, directly under your bust. Round to the nearest even number. This gives you your band size (e.g., 18). - Step 2: Measure Your Bust Size
Measure around the fullest part of your bust. Make sure the tape is level and not too tight. - Step 3: Calculate the Cup Size
Subtract the band size from your bust measurement. A 1-inch difference = A cup, 2 inches = B cup, and so on. Please note that these inch-based conversions may vary slightly depending on the brand or region.
What Are Sister Sizes for 18A?
Sister sizes are alternate bra sizes that have a similar cup volume. If 18A isn’t quite right, try these:
- 16B (slightly tighter band)
- 20AA (looser band)
Best Bra Styles for 18A
For smaller cup sizes with a larger band, comfort and subtle shaping are key. At The Foundation, we recommend:
- Lightly padded bras – add gentle shape without bulk
- Wireless bras – maximum comfort, especially for everyday wear. These are also ideal for sensitive skin or post-surgical recovery thanks to their gentle, non-restrictive design.
- Seamless styles – perfect under fitted tops
Featured Brands Available in 18A
We’ve curated high-quality bras in size 18A from trusted brands known for fit and craftsmanship:
- Chantelle – elegant French design with modern comfort
- Susa – supportive European engineering, known for soft cup construction and enhanced side support
- Triumph – beloved for its reliable fit and feel
- Berlei – classic Australian support and durability
- Anita – especially great for soft cup and wireless styles
Ready to Find Your Perfect Fit?
Explore our curated collection of 18A bras and discover comfort that empowers. From premium fabrics to flattering cuts, we’re here to support your everyday confidence.
Frequently Asked Questions
What is a size 18A in US sizing?
It's equivalent to a US 40A.
Can I wear 18A if I usually wear 16B?
Yes, 16B is a sister size with a tighter band and similar cup volume.
Is 18A a common size?
It’s less common but absolutely valid—many women need a larger band and smaller cup. At The Foundation, we stock this size regularly, so you can shop with confidence knowing your size is available.
How do I know if I’m wearing the wrong size?
If your band rides up or your cups gape or dig in, it’s time to reassess your fit using our fitting guide.
Can I return bras if they don’t fit?
Yes, visit our Orders & Returns page for eligibility and steps.