Lululemon and Athleta are the two dominant names in premium women's activewear, and the question shoppers ask most is simple: which one runs bigger? The short answer is that Athleta runs about half a size larger than Lululemon across leggings, tops, and sports bras — but the fit differences go deeper than just the numbers on the tag.
Leggings: the core comparison
Lululemon Align leggings in a size 6 measure roughly 27" waist and 36" hip. Athleta's Salutation Stash leggings in the same labeled size 6 measure closer to 28" waist and 37" hip — about an inch more room at the same number. Lululemon's compression is also noticeably firmer and more sculpting; Athleta uses a softer hand feel with more give through the waistband, which many shoppers find more comfortable for all-day wear rather than just a workout.
Side-by-side bottoms measurement table
| Lululemon Size | Lulu Waist / Hip | Athleta Size | Athleta Waist / Hip |
|---|---|---|---|
| 2 | 25" / 34" | XXS | 25" / 34.5" |
| 4 | 26" / 35" | XS | 26.5" / 35.5" |
| 6 | 27" / 36" | S | 28" / 37" |
| 8 | 28.5" / 37.5" | M | 29.5" / 38.5" |
| 10 | 30" / 39" | L | 31" / 40" |
| 12 | 32" / 41" | XL | 33" / 42" |
Sports bras: numeric vs. lettered sizing
Lululemon uses numeric sizes (2–14) tied to underbust and cup volume, while Athleta uses XS–XL with explicit cup-range labeling (A/B, C/D, D/DD). A Lululemon size 6 in a C/D cup is roughly equivalent to an Athleta Medium C/D, but Athleta's band tends to sit looser than Lululemon's at the equivalent size. If you're between sizes, the general rule is to size down at Athleta and size up at Lululemon for a comparable level of support.
Looking for a specific brand?
Fit varies far more between brands than between size systems.
Browse 30+ brand size charts| Lululemon Size | Underbust | Athleta Size | Underbust |
|---|---|---|---|
| 2 | 26"–27" | XXS | 26"–27" |
| 4 | 27"–28" | XS | 27"–28.5" |
| 6 | 28"–29" | S | 29"–30.5" |
| 8 | 29"–30" | M | 31"–32.5" |
| 10 | 31"–32" | L | 33"–34.5" |
| 12 | 33"–34" | XL | 35"–36.5" |
Tops and tanks
Athleta's tanks, like the Renew and Conscious Crop styles, fit true to a US 6–8 in a size Small. Lululemon's Swiftly and Align tanks fit closer to a US 4–6 at a numeric size 6. In practice, the same body that wears a Lululemon size 6 will usually land in an Athleta XS for a fitted top, or a Small for a relaxed style.
Inseams and length options
Both brands offer 23", 25", and 28" inseam options in most core legging styles, covering petite through tall heights reasonably well. Athleta goes further, stocking dedicated Petite (shorter rise plus a 21" inseam) and Tall (31" inseam) options across more of its lineup than Lululemon currently does — which is the main reason shoppers at the extremes of the height range tend to default to Athleta.
Fit notes and fabric feel
- Athleta is consistently noted for being more forgiving through the waistband and hips — a better starting point if you carry weight in the midsection.
- Lululemon's Align fabric is the closest thing either brand has to a "second skin" feel; its Wunder Train and Fast & Free lines run firmer and slightly smaller than Align at the same numeric size.
- Athleta's fabrics tend to have more mechanical stretch recovery over time, while Lululemon's Luon and Nulu fabrics can lose a small amount of compression after repeated washing.
Bottom line: how to convert your size
If you wear a Lululemon size 6, start at an Athleta size 4 or XS for fitted styles, or a size 6/S for relaxed styles. If you wear an Athleta Medium, expect to need roughly a Lululemon size 8. These are reliable starting points, but both brands publish garment measurements in inches and centimeters directly on each product page, and that number is always the most accurate signal — more accurate than the label itself.
For exact conversions across brands, check the Lululemon size chart alongside Athleta's own chart, or use the size converter to translate any body measurement into either brand's numbering. See also how to measure yourself for correct tape placement before you compare against these tables.
Return policies and fit risk
Because both brands ship internationally and their in-store stock varies by location, most shoppers end up ordering online and relying on returns to dial in fit. Lululemon and Athleta both offer free returns on unworn, tagged items within their standard return windows, which makes ordering two adjacent sizes and returning the one that doesn't work a low-risk way to nail down your true size in a new style, especially for first-time buyers of a specific silhouette.
Color and print availability by size
One practical difference shoppers notice: Lululemon frequently sells out of extended sizes (0–2 and 14+) in new colorways within days, while Athleta tends to keep a broader size range in stock for longer across its core styles. If you wear a size at either end of the range, checking stock early in a product launch matters more at Lululemon than at Athleta.