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18C

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Front close-up of The Foundation's Louise Underwire Low Necked Bra in Sequoia – detailed French embroidery and demi-cup shaping by Empreinte.
 
Front close-up of The Foundation's Louise Underwire Low Necked Bra in Sequoia – detailed French embroidery and demi-cup shaping by Empreinte.
Full model set in Louise Sequoia bra and culotte by The Foundation – showcasing matching embroidery and refined support by Empreinte.
Front view of Reve 3D Plunge Contour Bra Black, showing smooth underwired cups and plunge neckline
 
Front view of Reve 3D Plunge Contour Bra Black, showing smooth underwired cups and plunge neckline
Flat lay of Reve 3D Plunge Contour Bra Black, highlighting t-shirt bra shape and scalloped lace trim
Model wears Susa Latina Soft Bra Black from The Foundation – supportive wirefree bra with lace trim and cotton-lined cups.
 
Model wears Susa Latina Soft Bra Black from The Foundation – supportive wirefree bra with lace trim and cotton-lined cups.
Susa Latina Soft Bra Black flat lay from The Foundation – non-wired lace bra with 3-part supportive cup and flattering structure.
Front view of model wearing Gorgeous Maternity P Blusher Beige bra, highlighting wirefree design and comfortable fit
 
Front view of model wearing Gorgeous Maternity P Blusher Beige bra, highlighting wirefree design and comfortable fit
Back view  of Gorgeous Maternity P Blusher Beige maternity bra, showing adjustable straps and A-frame support
Front view of model wearing Ladyform Soft WX Bra Black by Triumph, showing full coverage and lace trim minimiser design
 
Front view of model wearing Ladyform Soft WX Bra Black by Triumph, showing full coverage and lace trim minimiser design
Full body shot of model in Ladyform Soft WX Bra Black, highlighting comfortable fit and adjustable straps
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True Shape N01 Wirefree Bra Black
True Shape N01 Wirefree Bra Black
Model wearing the Triumph Endless Comfort Wirefree Bra in Black, showcasing full-coverage fit—available at The Foundation.
 
Model wearing the Triumph Endless Comfort Wirefree Bra in Black, showcasing full-coverage fit—available at The Foundation.
Side view of the Endless Comfort Wirefree Bra in Black by Triumph, featuring wide padded straps—shop now at The Foundation.
Angled view of the Kiss of Cotton bra in Fresh Powder – Triumph’s wirefree classic with lace detail, available at The Foundation.
 
Angled view of the Kiss of Cotton bra in Fresh Powder – Triumph’s wirefree classic with lace detail, available at The Foundation.
Close up of the Kiss of Cotton Wirefree Bra in Fresh Powder, available at The Foundation – soft cotton blend with floral lace for everyday support.
Empreinte Melody Seamless Full Cup Bra in Caramel with underwire support and floral lace.
 
Empreinte Melody Seamless Full Cup Bra in Caramel with underwire support and floral lace.
front view of Empreinte Melody Bra Caramel showing satin straps and seamless fit.
Empreinte Louise Underwire Low-Necked Bra in Ombre Black with embroidered demi-cup and romantic detailing.
 
Empreinte Louise Underwire Low-Necked Bra in Ombre Black with embroidered demi-cup and romantic detailing.
Side angle of Louise Ombre Black bra showing sheer embroidered cups and underwire structure.
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Hedona Minimiser Bra Black
Hedona Minimiser Bra Black
Berlei Understate Wirefree Bra in Black—available at The Foundation, designed for everyday comfort and invisibility under clothes.
 
Berlei Understate Wirefree Bra in Black—available at The Foundation, designed for everyday comfort and invisibility under clothes.
Back view of the Berlei Understate Wirefree Bra in Black from The Foundation—features smoothing side bands and soft, secure straps.
Berlei Understate Wirefree Bra in Nude—find this comfy, invisible-fit bra for A-E cups, perfect for everyday support.
 
Berlei Understate Wirefree Bra in Nude—find this comfy, invisible-fit bra for A-E cups, perfect for everyday support.
Close up of Berlei Understate Wirefree Bra Nude—soft neckline and smooth lines for seamless wear under clothes.
model wearing Samanta Eteri Soft High Apex Bra in Anthracite, styled with jeans for a casual-chic look.
 
model wearing Samanta Eteri Soft High Apex Bra in Anthracite, styled with jeans for a casual-chic look.
Close up of Samanta Eteri Soft High Apex Bra Anthracite side detail – floral embroidery and structured lift.
Las Salinas Empire Green Full Cup Bra by PrimaDonna – vibrant neon embroidery on sheer mesh, front view on model.
 
Las Salinas Empire Green Full Cup Bra by PrimaDonna – vibrant neon embroidery on sheer mesh, front view on model.
Side profile of PrimaDonna’s Las Salinas Full Cup Bra – colourful floral lace detailing and statement straps.
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PrimaDonna Figuras Strapless Bra in Powder Rose – front view showing bandeau cut and seamless finish.
 
PrimaDonna Figuras Strapless Bra in Powder Rose – front view showing bandeau cut and seamless finish.
Model wearing Figuras Strapless Bra and brief set in Powder Rose – elegant and minimal full-body styling.
Front view of the PrimaDonna Deauville Bodysuit in Black, with lace cups and smoothing shape, available at The Foundation.
 
Front view of the PrimaDonna Deauville Bodysuit in Black, with lace cups and smoothing shape, available at The Foundation.
Flat lay of Deauville Bodysuit in Black by PrimaDonna, showing underwire design and elegant lace detailing, stocked by The Foundation.
Lifestyle image of model wearing the PrimaDonna Orlando Full Cup Bra in Crazy Blue, featuring shimmer embroidery, available at The Foundation.
 
Lifestyle image of model wearing the PrimaDonna Orlando Full Cup Bra in Crazy Blue, featuring shimmer embroidery, available at The Foundation.
Front view of the PrimaDonna Orlando Full Cup Bra in Crazy Blue, with full coverage and deep cups for lift and support, from The Foundation.
Model wearing PrimaDonna Orlando Full Cup Bra in Eye Shadow – styled for The Foundation’s signature comfort and elegance.
 
Model wearing PrimaDonna Orlando Full Cup Bra in Eye Shadow – styled for The Foundation’s signature comfort and elegance.
Front view of the PrimaDonna Orlando Full Cup Bra in Eye Shadow, shown on model for The Foundation.
Front view of Simone Perele Delice Full Cup Plunge Bra in Prestige Blue with embroidered cups and a flattering plunge neckline.
 
Front view of Simone Perele Delice Full Cup Plunge Bra in Prestige Blue with embroidered cups and a flattering plunge neckline.
Back view of the Delice Full Cup Plunge Bra in Prestige Blue showing U-shaped ballet back and fully adjustable wide straps.
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Caresse Soft Cup Bra Peau Rose
Caresse Soft Cup Bra Peau Rose
Simone Perele Karma 3D Plunge Bra in natural worn with briefs, available at The Foundation—soft lace and second-skin comfort for daily wear.
 
Simone Perele Karma 3D Plunge Bra in natural worn with briefs, available at The Foundation—soft lace and second-skin comfort for daily wear.
Front view of Karma 3D Moulded Bra in natural by Simone Perele, featuring scalloped lace and breathable cups—shop now at The Foundation.

18C Bra Size – Find Your Perfect Fit

Understanding 18C: A Perfect Fit Explained

Wearing the right bra size isn’t just about comfort—it’s about confidence. A proper 18C fit provides reliable support, shapes your silhouette beautifully, and helps you move through your day feeling secure and empowered. The 18C bra size is designed for those with a band size of 18 (measured around the ribcage, just under the bust) and a C cup, which reflects moderate bust volume. In Australian sizing, an 18C strikes a balance between firm support and a flattering silhouette, ideal for fuller figures seeking all-day comfort. This is a common cup size and fits comfortably into our bra size chart guidelines. Knowing your exact size helps eliminate digging straps, gaping cups, or discomfort.

International Size Equivalents

Region Equivalent Size
Australia / NZ 18C
UK / US / Canada 40C
EU (European Size) 90C
France (FR) 105C

Use our international bra size converter for easy comparison across regions.

Sizing Guide: Get Measured at Home

Grab a soft tape measure and follow these steps:

  • Band size: Measure snugly around your ribcage, directly under your bust. Round to the nearest even number in centimetres—that’s your back size.
  • Bust size: Measure around the fullest part of your bust, ensuring the tape is straight across your back.
  • Cup size: Subtract your band size from your bust measurement. A difference of 3 inches (about 7.5cm) indicates a C Cup.

Still unsure? Visit our in-store experts or explore our detailed Bra Fitting Guidelines online to get step-by-step advice and tips. You can also use our Bra Finder for personalised results tailored to your unique shape.

Sister Sizes to 18C

If you’re struggling to find your perfect fit or want alternatives, consider these sister size options. They offer the same cup volume but vary slightly in band size for a custom fit:

  • 16D (smaller band, larger cup)
  • 20B (larger band, smaller cup)
  • Size 18C/D (for those in-between sizes)

Best Bra Styles for 18C

Here are our top style picks for 18C bras, designed with your support and comfort in mind:

  • Wirefree Bra: Think soft, stretchy support with breathable materials—ideal for all-day wear.
  • T-Shirt Bra: Features seamfree construction and padded cups for a smooth, invisible silhouette under clothing.
  • Sports Bra: Whether you're walking or doing high-intensity training, our Low Impact to High Impact sports bras keep you supported. Look for wide shoulder straps, moulded cups, and hook and eye back opening.
  • Strapless Bra: Perfect for off-the-shoulder styles with reliable grip and a firm fit.
  • Push-Up Bras: Enhance your natural shape with lift and definition—great for a special outfit or everyday boost.
  • Fashion Bras: Add flair with styles that feature vintage-inspired lace or a shine floral knitted design.

Featured Brands in Size 18C

Our 18C collection features premium brands known for their fit, innovation, and style:

Support Meets Style

At The Foundation, we believe finding the right fit changes everything. Whether you're seeking a wirefree basic for everyday ease or a lace-detailed fashion piece for a night out, our 18C range offers something for every mood and moment. Explore bestsellers from brands like Berlei and Prima Donna, or find your new favourite with a quick browse. Enjoy fast delivery options and supportive returns policies.

Shop Now and embrace comfort and style today.

FAQs

How do I know if 18C is my correct bra size?

Use our tape measure method or consult our in-store fit experts.

Can I return a bra if it doesn’t fit?

Yes, as long as it's unworn and aligns with our returns policies.

Are there wirefree bras available in 18C?

Yes! We offer a range of wirefree bras in 18C, designed for day-long comfort without compromising on support. Check our collection page for current availability.

Which styles work best under T-shirts?

Go for a T-Shirt Bra with seamfree construction and light padding.

Where can I get help with fitting?

Visit our stores, contact us online, or try our Bra Finder.