Thinx

Thinx's sizing and absorbency, translated onto the same scale as every other brand - so you can shop it (or leave it) with a fair comparison.

Our take on Thinx

The original name in period underwear and still one of the highest claimed capacities, but it carries the most safety baggage - it settled the landmark PFAS class action. A capable product with a history worth understanding.

Best for

Shoppers who want a widely available, high-capacity brand and are comfortable reading its post-settlement testing.

Skip if

The PFAS history is a dealbreaker, or you want the widest size range (others go further).

What stands out

Among the highest capacities here: its current styles claim “up to 12 regular tampons’ worth” and no millilitre figure, which we compute as about 108 mL
The most recognized brand - easy to find and widely reviewed

Trade-offs

Settled a ~$5M PFAS class action in 2023, without admitting wrongdoing (see the note above)
Smaller live catalog than Knix or WUKA

Thinx and PFAS: an honest note

Thinx settled a class action for up to $5 million (reported January 2023) over marketing its underwear as safe and non-toxic while it allegedly contained PFAS "forever chemicals." Thinx did not admit wrongdoing, and the settlement resolved the marketing claims rather than a court ruling that the product is dangerous.

What the lawsuits and testing did and did not establish

How Thinx sizing runs

Runs true to size. Thinx states styles are "completely true to size" and recommends following the HIP measurement (measured at widest point, derriere included) for the most accurat

Size	Hip	Waist
XS	35–36"	25–26"
S	37–38"	27–28"
M	39–40"	29–30"
L	41–42"	31–32"
XL	43–44.5"	33–34.5"
X (plus)	43–44"	36–37"
1X	45–47"	38–40"
2X	49–51"	42–44"
3X	53–55"	46–48"
4X	57–59"	50–52"

Know your hip measurement? Get your size in every brand at once.

What Thinx's tiers really hold

Heads up: Thinx counts a 'regular tampon' as 9 mL, so its tampon labels look smaller per-tampon than brands using ~5 mL. Normalized to mL here for honest comparison. Separately, the brand's current flagship claim is 'up to 12 regular tampons' worth' with no millilitre figure published for the period line, and it is not reconcilable with the classic tier ladder below (Super = 45 mL). The identical phrase '12 regular tampons' worth' means 60 mL at WUKA, which states 5 mL per tampon and states 60 mL, and 72 to 108 mL at Thinx, which states no figure, across the FDA regular-tampon range of 6 to 9 g (21 CFR 801.430). v3 finding (2026-06-11): the SAME 'up to 12 regular tampons' worth' claim is printed on All Day PDPs, All Night PDPs, and Teens PDPs alike - one blanket maximum across the whole period line, with no per-tier capacity ladder in current product marketing. 2026-09-05 correction: the 'up to 100 mL' on how-they-work sits in the FAQ answer about light bladder leaks and belongs to the bladder-leak line (Thinx for All Leaks), not the period line; the 2026-06-10 verification misattributed it.

Light (legacy ladder)9 mL Data quality grade B, converted from tampon counts
Moderate (legacy ladder)18–27 mL Data quality grade B, converted from tampon counts
Heavy (legacy ladder)36 mL Data quality grade B, converted from tampon counts
Super (legacy ladder)45 mL Data quality grade B, converted from tampon counts
All Day108 mL Data quality grade B, converted from tampon counts
All Night108 mL Data quality grade B, converted from tampon counts
Overnight (Teens)108 mL Data quality grade B, converted from tampon counts

Claims verified 2026-09-05 · Catalog checked 2026-09-06 · Millilitres are the brand's own published claims, normalized - methodology. Cross-brand view: the full table.

Thinx catalog (32)

Thinx

All-Day Brief

All Day· 108 mLData quality grade B, converted from tampon counts

Sizes 9-10–15-16

$19

Our take on Thinx

How Thinx sizing runs

What Thinx's tiers really hold

Thinx catalog (32)

Your size and tier at this brand