Sports Bra Size Calculator

Need your regular bra size first? Use our bra size calculator.

The right sports bra eliminates bounce and stays in place through any workout. Finding your size starts with your regular bra measurements.

How Sports Bra Sizing Differs

Sports bra sizing differs from regular bra sizing because the primary design goal shifts from shape and aesthetics to motion control and support during physical activity. For a full breakdown of how these two bra types compare across support, materials, and health impact, see our sports bra vs regular bra comparison. A study published in the Journal of Sports Sciences found that unsupported breasts can move up to 15 centimeters during high-impact exercise, with vertical displacement causing ligament strain that accumulates over time. Sports bras address this through three construction methods: compression (pressing both breasts against the chest wall), encapsulation (individual cups that restrict each breast independently), and combination designs that use both approaches. The band in a sports bra should fit approximately one size snugger than a regular bra because the band provides 80% of structural support, and that proportion becomes critical when the body is in motion. Many sports bras use S/M/L sizing rather than band-and-cup, which maps roughly to band ranges: S covers 30-32, M covers 34-36, and L covers 38-40. Our bra size calculator provides your specific measurements so you can convert accurately to either system.

• The band should be snugger -- the band provides 80% of support, and that matters even more during movement. A firm band stops the bra from riding up mid-workout.
• Cup shape is different -- sports bras use compression, encapsulation, or a combination of both rather than traditional underwire construction.
• Sizing may differ by brand -- many sports bras use S/M/L sizing, which maps roughly to band ranges (S = 30–32, M = 34–36, L = 38–40). Our calculator gives you the specific band-and-cup size so you can convert either way. See our brand sizing guide for specific brand fit notes.

Support Levels Explained

Sports bra support levels are categorized into three tiers -- low, medium, and high impact -- based on the degree of breast displacement that occurs during specific activities. Research from the University of Portsmouth's breast biomechanics team, which has conducted over two decades of breast motion studies, shows that breast displacement during running averages 8 to 15 centimeters without adequate support, compared to 2 to 4 centimeters with a properly fitted high-impact sports bra. Low-impact activities like yoga and walking produce minimal vertical movement and require only light compression or a soft bralette-style sports bra. Medium-impact activities such as cycling, hiking, and strength training benefit from encapsulation designs that restrict side-to-side and forward motion. High-impact activities including running, HIIT, and jumping sports demand combination construction with both encapsulation cups and an outer compression layer. Cup size matters significantly for support selection: women wearing D cups and above generally require encapsulation or combination designs even for medium-impact activities, since compression alone cannot adequately control larger volumes during movement.

Different activities produce different levels of breast movement. Match your support level to your primary activity for the best combination of comfort and control.

When to Replace Your Sports Bra

Sports bra replacement is necessary when the elastic fibers in the band and fabric lose their recovery force, which typically occurs after approximately 72 wears or 6 to 12 months of regular use, whichever comes first. Unlike everyday bras where elastic degradation primarily affects comfort, a sports bra that has lost its compression directly reduces its ability to control breast displacement during exercise. The combination of sweat, heat, detergent, and repeated stretching breaks down spandex and elastane fibers at a faster rate than normal wear. According to sports bra manufacturers including Shock Absorber and Panache Sport, the primary indicator of replacement need is the return of noticeable bounce during activities that previously felt controlled. Other diagnostic signs include a band that no longer snaps back when stretched, straps that slip after being tightened to their shortest setting, and visible pilling or thinning of the compression fabric. Rotating between two or three sports bras extends the functional lifespan of each by allowing elastic fibers to recover between wears. Re-measuring every 6 months is also recommended because body composition changes from exercise can shift your sports bra size.

Re-check your sports bra size every 6 to 12 months, because that is also when you should replace the bra itself. Unlike regular bras, sports bras lose their compression and elasticity faster because of the repeated stress of high-movement activity. After approximately 72 wears, the elastic fibers in the band and straps break down with washing and sweat exposure.

If the band has lost its snap-back, the straps slip without adjustment, or you feel bouncing you didn't notice before, it's time for a new one. Rotating between two or three sports bras extends the lifespan of each.

For a detailed breakdown of how sports bras differ structurally from everyday bras, including fabric technology, support mechanisms, and when to choose each type, see our sports bra vs regular bra comparison. Your breast shape also determines which sports bra design works best -- compression suits round shapes, while encapsulation suits teardrop and bell shapes. Active teens should check our teen bra guide for age-appropriate sports bra recommendations.

Frequently Asked Questions