How to Measure Yourself for the Perfect Sports Bra Fit

Finding the right sports bra size is the foundation of getting proper support. Yet studies consistently show that up to 80% of women are wearing the wrong bra size—and sports bras are no exception. Taking accurate measurements at home is the first step toward finding a sports bra that truly works for you. This guide walks you through the complete measuring process with specific guidance for Australian sizing.

What You'll Need

Before you begin, gather a soft measuring tape (the flexible kind used for sewing, not a rigid metal tape measure). If you don't have one, a piece of string or ribbon marked against a ruler can work in a pinch. You'll also want a mirror to help ensure the tape is level, and it's helpful to wear a non-padded, well-fitting bra during measurement—or no bra at all.

Step 1: Measure Your Band Size

The band measurement is taken around your ribcage, directly under your breasts where a bra band would sit. This measurement is crucial because the band provides the majority of a sports bra's support.

How to Measure:

1. Stand straight with your arms relaxed at your sides.
2. Wrap the measuring tape around your ribcage, directly under your bust.
3. The tape should be parallel to the floor all the way around—use a mirror to check.
4. The tape should be snug but not tight. You should be able to breathe normally, and the tape shouldn't dig into your skin.
5. Round to the nearest whole number. If you measure an odd number (like 77 cm), round to the nearest even number (78 cm) for the band size.

Converting to Australian Band Size:

In Australia, band sizes are numbered rather than measured in inches. Here's how your measurement converts:

• 63-67 cm = Size 8
• 68-72 cm = Size 10
• 73-77 cm = Size 12
• 78-82 cm = Size 14
• 83-87 cm = Size 16
• 88-92 cm = Size 18
• 93-97 cm = Size 20

Step 2: Measure Your Bust

The bust measurement is taken at the fullest part of your breasts. This measurement, combined with your band measurement, determines your cup size.

How to Measure:

1. Wrap the tape around your body at the fullest part of your bust—typically at nipple level.
2. Keep the tape parallel to the floor and avoid pulling it tight. The tape should rest gently against your skin.
3. If your breasts are asymmetrical (which is completely normal), measure at the point where your larger breast is fullest.
4. Note your measurement in centimetres.

Step 3: Calculate Your Cup Size

Your cup size is determined by the difference between your bust measurement and your band measurement. Subtract your band measurement (in cm) from your bust measurement (in cm), then use this guide:

• 10-12 cm difference = A cup
• 12-14 cm difference = B cup
• 14-16 cm difference = C cup
• 16-18 cm difference = D cup
• 18-20 cm difference = DD/E cup
• 20-22 cm difference = E/F cup
• 22-24 cm difference = F/FF cup
• 24-26 cm difference = G cup

For example, if your underbust measures 75 cm (Size 12 band) and your bust measures 91 cm, the difference is 16 cm, indicating a D cup. Your calculated size would be 12D.

Understanding Sister Sizes

Sister sizes are bra sizes with the same cup volume but different band and cup combinations. Understanding sister sizes helps when a brand runs small or large, or when your exact size isn't available.

Here's how it works: if you wear a 12D, your sister sizes are 10DD (smaller band, larger cup letter) and 14C (larger band, smaller cup letter). The cup volume remains the same, but the band fit changes.

For sports bras, it's usually better to size down in the band (the sister size with a smaller band and larger cup letter) rather than up. This is because sports bras need to be snugger than everyday bras to provide adequate support during movement.

Sports Bra Sizing Differences

Many sports bras use simplified sizing (XS, S, M, L, XL) rather than traditional band and cup sizing. While this is convenient, it can make finding the right fit more challenging. Here's how to navigate it:

Sizing Charts

Always check the specific brand's sizing chart before purchasing. A "Medium" at one brand might fit very differently than a "Medium" at another. Most brands provide both band/cup size equivalents and body measurements for each size.

When Sizes Don't Match

If your band size suggests one size and your cup size suggests another, prioritise cup coverage for low-impact activities and band fit for high-impact activities. For example, if you're between a Medium (suggested by your band) and a Large (suggested by your cup), choose the Large for yoga but try the Medium for running—the tighter band may provide better high-impact support even if the cups are slightly less generous.

Testing the Fit

Once you have a sports bra in your calculated size, use these checks to verify the fit:

The Band

• The band should sit level around your body, parallel to the floor
• It should feel snug but not painfully tight—you should be able to fit two fingers under the band but not more
• The band shouldn't ride up when you raise your arms or move around
• There shouldn't be any gaps or puckering at the back

The Cups

• Your breast tissue should be fully contained within the cups
• No spillage at the top, sides, or center
• No gaps or wrinkling in the cup fabric
• The center gore (between the cups) should sit flat against your sternum

The Straps

• Straps should feel secure without digging in
• They shouldn't slip off your shoulders during movement
• You should be able to fit one or two fingers under each strap comfortably

The Bounce Test

Jump up and down vigorously several times. If you notice significant bounce or discomfort, you need more support—either a different size or a higher support level.