You deserve a sports bra that matches your power. If you’ve ever cut a run short, skipped burpees, or double‑layered tops because of bounce or chafe, this sports bra size and support guide is for you. Below, we translate lab‑tested insights into clear steps so you can pick the right support level, dial your fit in minutes, and feel unstoppable—whether you’re lifting, hiking, or flowing through vinyasa.

The quick answer

If you train hard or move fast, prioritize support first, then refine size and features. For low‑impact days (yoga, mobility), light to medium support is fine; for running, HIIT, and court sports, choose high support with either encapsulation or hybrid construction. Then confirm your size with an underbust/overbust check and a five‑point fit test. Finally, match fabric and straps to your sweat rate and preferred moves. University of Portsmouth research shows proper support improves comfort and mechanics; poor support can shorten stride and increase effort, while excessive restriction may have downsides for the back during high‑impact work. See the research overview and fit guidance.

Sports bra types and support levels

Support style is the foundation of bounce control.

• Compression: a single panel hugs both breasts to the chest wall. Best for smaller cup sizes and low‑to‑moderate impact.
• Encapsulation: individual cups support each breast. Typically better for larger cup sizes and higher impact.
• Hybrid: combines encapsulation cups with compressive overlays or panels for maximum control.

Peer‑reviewed testing on nearly 100 bras found bounce reduction spans a wide range (about 36–74%). Key features that raise support include encapsulation styles, padded cups, adjustable underbands, higher necklines, and certain fiber blends. Translation: for runs and jump‑heavy training, look for structured cups plus fine‑tuning at the band and straps. For studio days, light compression can be perfect. See the Ergonomics study summary.

Measure your size in two minutes

Toss the guesswork—use quick measurements to find a starting size.

1. Measure your underbust: wrap a tape snugly around your ribcage, directly under the bust. Round to the nearest whole inch/centimeter. That’s your band baseline.
2. Measure your overbust: wrap the tape around the fullest part of your bust, level across the back.
3. Calculate your starting size: use your brand’s chart to map the difference between overbust and underbust to a cup, then pair it with the closest band size that feels firm without digging.
4. Reality‑check with a “best‑fit” approach: most support should come from the band, not the straps. If the band rides up, it’s too loose; if breathing feels restricted, it’s too tight. Enclose tissue fully in the cups—no gaping, no spillage, center panel resting lightly against the sternum on wired styles.

Why this matters: researchers report many women wear the wrong size, and fit—not the tag—is what determines comfort and performance. Portsmouth’s fit criteria and performance takeaways are an excellent reference.

The five‑point fit test (do this in the mirror)

Use these checks to confirm your sports bra size before you hit the gym.

1. Band: level around your torso, firm enough that you can slide two fingers underneath. It shouldn’t migrate when you raise your arms.
2. Cups: tissue sits fully inside with smooth coverage; no quad‑boob or gaping.
3. Center panel (if present): rests against the sternum without digging.
4. Straps: adjust for lift without creating shoulder grooves; more than ~5 cm of stretch usually means you’ll bounce.
5. Move test: jump, jog in place, and twist. You want secure control without restriction or hot spots.

Pro tip: Sport‑specific support feels different than everyday bras. Evaluate it by movement, not just by how it looks.

Match support to activity—without over‑restricting

• Low impact (yoga, Pilates, mobility): light to medium support; soft straps and breathable fabrics prioritize comfort and range of motion.
• Moderate (strength, cycling, hiking): medium to high support; encapsulation or hybrid styles shine when you mix lifts with cardio bursts.
• High (running, HIIT, court/field): high support with encapsulation or hybrid designs, higher necklines, and adjustable bands.

Balance is key. Emerging research suggests that chasing 100% bounce elimination could increase spinal loading during running. You still want firm support for impact, but avoid straitjacket‑tight fits that fight your breathing and mechanics. Aim for security plus mobility. Read the 2025 back‑load study summary. For practical selection tips by impact and body type, the American Council on Exercise also emphasizes fit, activity matching, and ventilation. ACE guidance here.

Fabric, breathability, and features that matter

• Fabrics: moisture‑wicking synthetics (poly, nylon) with elastane keep you drier and reduce friction. For hot classes, prioritize lighter knits and mesh panels.
• Strap geometry: racerback increases anchor points; wide or cushioned straps help disperse load. Front‑adjustable straps make mid‑workout tweaks easy.
• Closures: hook‑and‑eye bands and front zips enable a firmer band fit without wrestling the bra on and off.
• Necklines: higher fronts can help reduce vertical motion on high‑impact days.
• Pockets: on trails or long sessions, stash a key or gel without relying on waistbands.

Care and replacement

Sweat, heat, and stretch break down elastic. Wash bras in cool water, skip fabric softeners (they clog wicking fibers), and air‑dry. Replace when the band feels loose on the tightest hook, straps have lost recovery, or support no longer feels dialed. As a rule of thumb, ACE suggests most sports bras are ready for retirement in roughly 6–12 months depending on frequency and intensity. See ACE’s practical advice.

Inclusive fit tips (because bodies vary)

• Fuller busts: favor encapsulation or hybrids with adjustable underbands and straps; a higher neckline helps keep motion controlled without over‑tightening.
• Smaller busts: light‑to‑medium compression can feel effortless for studio or strength work; size up or choose encapsulation for sprints.
• Broad shoulders or mobility limits: look for front zips or bands with back closures to avoid wrestling pull‑overs.
• Skin sensitivity: choose softer knits and seam placements away from high‑friction zones; skip softeners and test new styles during shorter sessions first.
• Postpartum changes: re‑measure and retest—size and support needs can shift month to month.

Try these from Girl Power Gear

• Build your kit from our Ultimate Sports Bra Gear collection—options for light days to high‑impact sessions.
• Want more coverage and stability under straps? Our Recycled Longline Sports Bra adds bandwidth for comfort without sacrificing support.

• Prefer matching sets or need squat‑proof bottoms to pair with your bra? Explore Leggings & Pants Gear for compressive fits that stay put.

FAQs

How tight should a sports bra feel? Firm, not breath‑stealing. Most support should come from the band; you should breathe and rotate freely while feeling stabilized.

Do I need different bras for different sports? Often, yes. Keep at least one high‑support option for running/HIIT and a softer, breathable option for yoga or recovery days.

Are high‑support bras ever “too much”? If a bra feels restrictive or changes your breathing mechanics, try a slightly less compressive style or a size/strap adjustment. Early evidence suggests over‑restricting bounce isn’t always better for the back during high‑impact running, so aim for secure but mobile support. Study summary here.

Compression vs. encapsulation—how do I pick? Smaller bust + low impact: compression is often comfy and efficient. Larger bust or high impact: encapsulation/hybrid wins. Feature cues like adjustable bands and higher necklines correlate with better control in testing. Details from lab work.

What’s the fastest way to sanity‑check size at home? Use the underbust/overbust method, then run the five‑point fit test. Don’t chase tag numbers—prioritize comfort and motion control validated by a quick jump test. For deeper context and fit pointers, explore Portsmouth’s expert guidance.

Ready to train without distraction? Build your high‑impact pick from our Ultimate Sports Bra Gear, then finish the kit with supportive leggings. You bring the grit; we’ll bring the gear.