There is a specific kind of frustration that comes with a sports bra that just doesn't work. Whether the straps are digging into your shoulders during a long run or the band feels like it’s sliding up every time you reach for a pull-up bar, the culprit is almost always a fit issue. Most women are wearing the wrong bra size, often settling for "close enough" and sacrificing both comfort and performance in the process.
At Senita Athletics, we design our sports bras to be the most reliable part of your gym bag. To get that "set it and forget it" feel, you need to start with accurate measurements. This guide will walk you through how to find your true size using our specific fit standards.
Why Precise Measurements Matter
It might seem easier to just grab the same size you wear in a daily t-shirt bra, but sports bras function differently. They are high-performance equipment designed to minimize breast movement and protect the Cooper’s ligaments—the connective tissues that prevent sagging.
Taking a few minutes to measure properly ensures your bra can do its job: minimizing bounce and preventing exercise-induced discomfort.
Step 1: Measure Your Band Size
The band provides about 80% of a bra’s support, so getting this number right is the most important step.
- Prepare: Stand in front of a mirror wearing your thinnest, non-padded bra (or nothing at all).
- Position: Stand with your feet hip-distance apart and wrap a soft measuring tape around your ribcage, directly under your bust where a bra band usually sits.
- Check the Level: Ensure the tape is parallel to the ground all the way around your back. If it’s slanted, your measurement will be too large.
- The Fit: Be careful not to "flare" your ribs or hold your breath while measuring. Pull the tape snug against your skin but not so tight that it digs in. You should be able to take a normal breath.
Record this number in inches. Because the Senita size guide accounts for half-inch increments, record your measurement to the nearest half-inch (e.g., 31.5 or 32).
Step 2: Measure Your Bust Size
Next, you need to find the measurement of the fullest part of your chest to determine your cup volume.
- Position: Find the widest part around your bust and wrap the tape around that point. This is usually across the center of the nipples.
- The Tension: Keep the tape level around your back. Unlike the band measurement, the tape should be slightly looser here. You want it to rest on top of the tissue without compressing or squishing it.
- Note the Number: Record this measurement in inches to the nearest half-inch.
Step 3: Calculate Your Senita Size
To find your fit, compare your Band Measurement and your Bust Measurement against the Senita size matrix. This helps determine the appropriate volume and support level for your frame.
Using the Senita Athletics Size Chart
Because our bras use high-performance compression fabrics like our Lux or Skin blends, our sizing sometimes uses alpha sizes (XS–XXL) instead of traditional wire-bra numbers. Once you have your band and bust measurements, use the chart below to find your Senita fit.
Senita Bra Size Matrix
| Band Measurement | 31-33.5" (Bust) | 34-35.5" | 36-37.5" | 38-39.5" | 40-41.5" | 42-43.5" | 44-46" |
|---|---|---|---|---|---|---|---|
| 24 | XS | XS | XS | XS/S | S | S/M | - |
| 26 | XS | XS | XS | S/M | S/M | M | M |
| 28 | XS/S | XS/S | S/M | S/M | S/M | M/L | M/L |
| 30 | XS/S | XS/S | S/M | M/L | M/L | L/XL | L/XL |
| 32 | S/M | S/M | M/L | M/L | M/L | L/XL | L/XL |
| 34 | - | M/L | M/L | M/L | L/XL | L/XL | L/XL |
| 36 | - | - | L/XL | L/XL | L/XL | XL/XXL | XL/XXL |
| 38 | - | - | - | L/XL | L/XL | XL/XXL | XL/XXL |
| 40 | - | - | - | - | XL/XXL | XL/XXL | XXL |
For more information and sizing charts, visit our full Size Guide.
Finding the Right Support for Your Workout
Not every workout requires the same level of compression. Matching your bra to your activity level extends the life of your gear and keeps you comfortable.
- Low Impact: Best for yoga, Pilates, or walking. These bras prioritize mobility and a "barely-there" feel. Check out our athletic tops for options with light built-in shelves.
- Medium Impact: Ideal for cycling, weightlifting, or power walking. These provide a secure hold without being overly restrictive.
- High Impact: Essential for running, HIIT, or jumping rope. These are engineered to eliminate bounce and usually feature wider, padded straps and higher necklines.
- Maternity & Nursing: Pregnancy and postpartum require extra flexibility. Our nursing sports bras feature easy-access clips and soft fabrics to accommodate fluctuating sizes.
Common Fitting Mistakes to Avoid
- The "Hiking" Band: If your band is pulling up in the back, it is likely too big. A supportive band should sit level across your back, anchored under your shoulder blades.
- The Double Boob: If you are spilling out over the top or sides of the fabric, you likely need to go up in bust size.
- Strap Digging: If your straps are leaving red marks, you are likely relying on them for support rather than the band. Try a smaller band size.
- The Finger Test: You should be able to fit two fingers under the band comfortably. If you can fit more, it's too loose. If you can't fit any, it's too tight.
Ordered a bra that doesn't sit quite right? Don't settle for "good enough". All domestic orders are eligible for swaps if you need a different size or a completely different product. Sizing exchanges are free of charge, and we handle the shipping costs both ways. We will simply adjust your final total to reflect any price difference between the items.
Find Your Strength in the Perfect Fit
A great sports bra should feel like a firm hug that moves with you. By taking the time to measure your band and bust accurately, you move away from the guesswork and toward a more productive, distraction-free workout. At Senita, we focus on moisture-wicking fabrics and thoughtful design so that once you find your fit, you can focus entirely on your goals.
Frequently Asked Questions
How tight should my sports bra be?
It should be snug enough to stay in place during movement but not so tight that it restricts your breathing. You should always be able to take a full, deep breath without feeling constricted.
How often should I replace my sports bra?
Even high-quality elastics eventually lose their "snap." If you find yourself tightening the straps more often or notice the band sliding around, it’s usually time for a replacement—typically every 6 to 12 months depending on use.
Should I size down for more support?
We don't recommend sizing down purely for support. Instead, look for a bra specifically designed for "High Impact." Sizing down usually leads to discomfort and restricted mobility rather than better stability.
What if I am between sizes on the Senita chart?
If your measurements fall between two sizes, consider your personal preference. If you like a very locked-in, compressive feel, go with the smaller size. If you prefer a bit more room for comfort, choose the larger size.
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About the Authors: Maddie and Jenna
Sisters, moms, and lifelong athletes, Maddie and Jenna founded Senita Athletics in 2015 with a scrappy determination to make high-performance activewear affordable for every woman. Their expertise is rooted in experience; both spent four years competing in Division I collegiate cross country and track and field, giving them a deep understanding of how gear needs to perform under pressure.
From packing orders during naptime to navigating the global sale and eventual repurchase of the brand in 2025, their journey has always been fueled by one thing: Sisterhood. Today, they are back at the helm, personally ensuring that every stitch supports the busy, active lives of the community they love.