PeriodFinder

Absorbency, normalized

How much does period underwear actually hold?

Every brand measures absorbency in “tampons,” but each one defines it differently, and nobody publishes the neutral comparison. We normalized 13 brands onto one objective scale: millilitres.

A tier LABELED 'Heavy' ranges from ~20 mL (Saalt, Proof, WUKA) to ~36-63 mL (Knix) across brands - roughly a 3x spread for the same word. A shopper buying 'Heavy' has no way to know which she is getting.

Updated 2026-09-20 · Every number is graded for data quality (A/B/C) · How we built this table · Our own bench test · The 2026 claims report · Download the dataset (JSON, CC BY 4.0) · Printable cheat-sheet

By PeriodFinder, Editorial team

A tier labeled “Heavy” isn't the same thing twice

BrandIts “Heavy” tier holdsIn tampon-equivalentsData quality
Saalt20 mL4converted from tampon countsData quality grade B, converted from tampon counts
Proof (Proof by Always)20 mL4converted from tampon countsData quality grade B, converted from tampon counts
Bambody20 mL4converted from tampon countsData quality grade B, converted from tampon counts
WUKA20 mL4brand publishes mLData quality grade A, brand publishes mL
Thinx36 mL7.2converted from tampon countsData quality grade B, converted from tampon counts
Aisle40 mL8brand publishes mLData quality grade A, brand publishes mL
The Period Company45 mL9converted from tampon countsData quality grade B, converted from tampon counts
Knix36–63 mL7.2–12.6the brand's own pages differ; range shownData quality grade C, the brand's own pages differ; range shown

Want about 40 mL of real coverage? Here's the tier you need in each brand

The same real capacity is called “Moderate” at one brand and “Super Heavy” at another. That's the gap this tool closes.

  • Knix
    Heavy(36–63 mL)Data quality grade C, the brand's own pages differ; range shown
  • Thinx
    All Day(108 mL)Data quality grade B, converted from tampon counts
  • Modibodi
    Super(50 mL)Data quality grade A, brand publishes mL
  • Saalt
    Super(40–50 mL)Data quality grade B, converted from tampon counts
  • Proof (Proof by Always)
    Overnight (Hi-Rise / Boyshort)(45 mL)Data quality grade B, converted from tampon counts
  • The Period Company
    Heavy(45 mL)Data quality grade B, converted from tampon counts
  • Bambody
    Heavy Flow(20 mL)Data quality grade B, converted from tampon counts
  • Aisle
    BOOST (adjustable, +BOOSTER insert)(20–40 mL)Data quality grade B, converted from tampon counts
  • WUKA
    Super Heavy(60 mL)Data quality grade A, brand publishes mL
  • Rael
    Reusable Boyshort(15–25 mL)Data quality grade C, the brand's own pages differ; range shown
  • Hanky Panky
    Regular(15 mL)Data quality grade B, converted from tampon counts
  • Skims
    Period Panties Brief(15 mL)Data quality grade B, converted from tampon counts

Every brand, every tier

Data quality grades: A = the brand publishes mL directly · B = converted from the brand's tampon counts · C = the brand's own sources conflict or the claim isn't first-party confirmed. Full methodology

Knix

claims verified 2026-06-11

Note: Knix's blog and live collection pages publish different super-tampon counts per tier; this table uses the live collection-page (higher) figures.

  • Light 5–15 mL Data quality grade B, converted from tampon counts
  • Moderate 18–36 mL Data quality grade C, the brand's own pages differ; range shown
  • Heavy 36–63 mL Data quality grade C, the brand's own pages differ; range shown
  • Ultra 63–99 mL Data quality grade C, the brand's own pages differ; range shown

Thinx

claims verified 2026-09-05

Note: Thinx gives one claim for its whole period line, 'up to 12 regular tampons' worth', and counts a regular tampon as 9 mL, so we show about 108 mL for every current style (computed from the claim, grade B).

Modibodi

claims verified 2026-06-11
  • Light 20 mL Data quality grade A, brand publishes mL
  • Moderate 30 mL Data quality grade A, brand publishes mL
  • Super 50 mL Data quality grade A, brand publishes mL

Saalt

claims verified 2026-06-11
  • Light 10 mL Data quality grade B, converted from tampon counts
  • Regular 15 mL Data quality grade B, converted from tampon counts
  • Heavy 20 mL Data quality grade B, converted from tampon counts
  • Super 40–50 mL Data quality grade B, converted from tampon counts

Proof (Proof by Always)

claims verified 2026-06-10
  • Super-Light 5 mL Data quality grade B, converted from tampon counts
  • Light 5 mL Data quality grade B, converted from tampon counts
  • Moderate 15 mL Data quality grade B, converted from tampon counts
  • Heavy 20 mL Data quality grade B, converted from tampon counts
  • Super-Heavy 25 mL Data quality grade B, converted from tampon counts
  • Overnight (Super Heavy Brief) 35 mL Data quality grade B, converted from tampon counts
  • Overnight (Hi-Rise / Boyshort) 45 mL Data quality grade B, converted from tampon counts

Ruby Love

claims verified 2026-06-05
  • Period underwear (one level) no longer published by the brand

The Period Company

claims verified 2026-06-11
  • Light (Thong) 10 mL Data quality grade B, converted from tampon counts
  • Medium 20 mL Data quality grade B, converted from tampon counts
  • Heavy 45 mL Data quality grade B, converted from tampon counts

Bambody

claims verified 2026-09-20
  • Light Flow 5–10 mL Data quality grade C, the brand's own pages differ; range shown
  • Heavy Flow 20 mL Data quality grade B, converted from tampon counts

Aisle

claims verified 2026-06-05

WUKA

claims verified 2026-06-10
  • Light 7 mL Data quality grade C, the brand's own pages differ; range shown
  • Medium 15 mL Data quality grade A, brand publishes mL
  • Heavy 20 mL Data quality grade A, brand publishes mL
  • Super Heavy 60 mL Data quality grade A, brand publishes mL

Rael

claims verified 2026-06-05

Note: Product page says 4-5 regular tampons; blog/retailer says 3.

  • Reusable Boyshort 15–25 mL Data quality grade C, the brand's own pages differ; range shown

Hanky Panky

claims verified 2026-06-11
  • Light 10 mL Data quality grade B, converted from tampon counts
  • Regular 15 mL Data quality grade B, converted from tampon counts

Skims

claims verified 2026-06-10

What these numbers are, and what they aren't

All figures are the brands' OWN maximum-capacity claims (typically saline lab tests at full saturation). The only published test with real blood components (DeLoughery et al., BMJ Sexual & Reproductive Health, 2023) poured packed red blood cells slowly onto three pairs of one unnamed brand's super-absorbency period underwear until the blood pooled; they held under 3 mL each, 2 mL on average. That measures one product under a continuous pour, and the authors note capacity may be greater with a slower flow. It is a different thing from a brand's saline-test maximum, not a ranking of any brand's claim. Blood is more viscous than saline and real wear is not a lab, so use this table to compare brands on a like-for-like basis and read no mL figure as a leak-free guarantee.

Capacity is normalized to objective millilitres (1 regular tampon ≈ 5 mL; 1 super ≈ 9 mL), because brands disagree on what a “tampon” means. Swimwear, reusable pads, removable inserts and bladder-leak lines are excluded. Figures are taken from each brand's own published claims; where a brand's own pages conflict, it's flagged above. Read the full methodology for conversion rules, sources, and the corrections policy.

Turn the table into your answer

This page is every brand's claim made comparable. The tools turn it into the tier and the size that fit you, in your browser.

What absorbency do I need?Find my size in every brand