Why people look at alternatives
The practical reasons are the usual ones: fit that never settled (reviews often suggest sizing up in the leakproof styles), a tier that did not hold what you expected (Knix's "Heavy" claims 36 to 63 mL, while other brands' "Heavy" can be 20 mL, so a downgrade can surprise you), or price. The picks below carry live prices and verified millilitres so you can see exactly what a switch trades away.
Some people also look elsewhere after the brand's 2023 PFAS marketing settlement, which Knix settled without admitting wrongdoing. What it did and did not establish is in our PFAS guide. If safety drives your switch, judge every brand, including the one you switch to, by its current published testing rather than its marketing words.
Mind the capacity ceiling when you switch
One thing to know before you switch: by claimed maximums, only Thinx's current styles match or exceed Knix's Ultra (up to about 99 mL, the highest figure any brand states in millilitres). Thinx states "up to 12 regular tampons' worth" and no millilitre figure at all; that works out to about 108 mL on the FDA regular-tampon ceiling. Every other brand we track tops out lower. If you wore Ultra for genuinely heavy days, your realistic alternatives are Thinx at the top of the range, or doubling up with a backup on peak days at any other brand. If you wore Knix's lighter tiers, nearly every brand covers you.
Quick answers
- What is similar to Knix?
- For everyday tiers, WUKA, Saalt, Modibodi, Thinx, and The Period Company all publish verified claims in the same 20 to 60 mL band as Knix's core range. For Knix's Ultra tier specifically (up to about 99 mL claimed), the only comparable ceiling in our catalog is Thinx's current styles at roughly 108 mL, a figure we compute from its 12-regular-tampon claim rather than one Thinx publishes. The ranked list above shows current stock.
- Why did Knix change its PFAS claims?
- As part of its 2023 class-action settlement, Knix agreed to make "PFAS-free," "toxic-chemical-free" and "fluorine-free" claims only with testing behind them, and to increase PFAS testing for two years. It admitted no wrongdoing. So the absence of those words on Knix's site today is a settlement term, not necessarily a change in the product. The details are in our PFAS guide.
- Is anything more absorbent than Knix Ultra?
- In our catalog only Thinx's current styles sit at or above Knix Ultra's roughly 99 mL ceiling, at about 108 mL - and that one is our computation from Thinx's "up to 12 regular tampons' worth," not a figure Thinx publishes. Both numbers are saline-lab maximums, so treat them as a comparison scale, not a guarantee.
- Do Knix sizes match other brands?
- No - every brand draws its own chart, and a Knix size is only a starting guess elsewhere. Use your hip measurement in the size finder to get your size at every charted brand at once, including a note on which brands run small or large.
Related guides
PFAS in period underwear: the lawsuits, the testing, and what it actually means
What PFAS "forever chemicals" are, the Thinx and Knix class-action settlements, the independent lab testing, and what was established and what was not.
Thinx alternatives: what to buy instead, by the numbers
Every in-stock alternative to Thinx from the brands we track, ranked by verified millilitres, with the usual reasons people switch and how to compare.
What size period underwear should I get?
Period underwear is sized on your hip measurement, not your dress size, and brands disagree: one body can be a M here and an L there. How to get it right.
Want the one-page version of the data behind these guides? The printable absorbency cheat-sheet puts every brand's tiers in millilitres on a single sheet - free, no email needed.
See every alternative with live prices
The full catalog filters by capacity and brand, with weekly-checked prices and stock - or compare Knix head-to-head with any brand we track.