{"name":"PeriodFinder cross-brand period-underwear absorbency dataset","description":"Each period-underwear brand's own published absorbency claim, normalized to a single objective scale in millilitres, with a data-quality grade, the source, and the brand's verification date. No brand publishes this neutral cross-brand comparison. Figures are normalized brand CLAIMS, not independent lab measurements.","units":"millilitres","version":"2026-09-20","updated":"2026-09-20","spine_revision":3,"source_url":"https://www.periodfinder.com/absorbency","methodology_url":"https://www.periodfinder.com/absorbency/methodology","self_url":"https://www.periodfinder.com/absorbency/data.json","license":"https://creativecommons.org/licenses/by/4.0/","license_name":"CC BY 4.0","attribution":"PeriodFinder, https://www.periodfinder.com/absorbency","citation":"PeriodFinder, \"Cross-Brand Period Underwear Absorbency (millilitres)\", https://www.periodfinder.com/absorbency","independent_measurement":{"finding":"Three pairs of one unnamed brand’s super-absorbency period underwear held under 3 mL each, 2 mL on average, of packed red blood cells poured slowly until the blood pooled, in the only published test with real blood components.","underwear_pairs_tested":3,"underwear_brand":"not named by the authors","underwear_absorbency_tested":"super absorbency (sizes S, M, L)","products_tested_all_categories":21,"ml_each_max":3,"ml_each_mean":2,"test_medium":"expired human packed red blood cells, poured slowly until pooling","scope":"One product under a continuous pour; the authors note period underwear may hold more with a slower flow. A different measurement from a brand’s saline-test maximum, not a ranking of any brand’s claim.","source":"DeLoughery E, Colwill AC, Edelman A, Samuelson Bannow B. \"Red blood cell capacity of modern menstrual products: considerations for assessing heavy menstrual bleeding.\" BMJ Sexual & Reproductive Health, published online 7 August 2023.","source_url":"https://doi.org/10.1136/bmjsrh-2023-201895"},"normalization_basis":"One regular tampon holds about 5 mL unless the brand states its own basis, anchored on the FDA 21 CFR 801.430 tampon absorbency ranges.","data_quality_grades":{"A":"the brand publishes millilitres directly","B":"converted from the brand's own tampon-equivalent claim","C":"conflicting or unconfirmed"},"key_facts":["A tier labeled \"Heavy\" spans roughly 20 to 63 mL across brands, so \"Heavy\" alone does not tell a shopper how much a pair holds.","The identical phrase \"12 regular tampons' worth\" means about 60 mL at WUKA, which states 5 mL per tampon and states the 60 mL, but up to about 108 mL at Thinx, which states no millilitre figure for its period underwear (our computation at the FDA regular-tampon ceiling, 21 CFR 801.430).","These are normalized brand claims, not independent lab measurements; grades A/B/C mark how each number was derived.","The only published test with real blood components (BMJ Sexual & Reproductive Health, 2023) poured blood slowly onto three pairs of one brand’s super-absorbency underwear until it pooled; they held under 3 mL each, 2 mL on average. One product, one method, and a different measurement from a saline-test maximum, so it does not rank any claim here.","Thinx publishes no millilitre figure for its period underwear; its 108 mL row is computed from \"up to 12 regular tampons' worth\" at the FDA regular-tampon ceiling of 9 g (21 CFR 801.430) and carries grade B for that reason."],"brand_count":13,"brands":[{"brand":"Knix","basis":"super tampons x9 mL; uses live collection-page figures (higher than the brand's own blog)","verified":"2026-06-11","tiers":[{"tier":"Light","ml_min":5,"ml_max":15,"regular_tampon_equiv_min":1,"regular_tampon_equiv_max":3,"grade":"B","source":"1-3 regular tampons (ladder re-confirmed on live PLP 2026-06-11)","legacy":false,"retracted":false},{"tier":"Moderate","ml_min":18,"ml_max":36,"regular_tampon_equiv_min":3.6,"regular_tampon_equiv_max":7.2,"grade":"C","source":"2-4 super tampons (collection page, re-confirmed 2026-06-11; blog says 2-3)","legacy":false,"retracted":false},{"tier":"Heavy","ml_min":36,"ml_max":63,"regular_tampon_equiv_min":7.2,"regular_tampon_equiv_max":12.6,"grade":"C","source":"4-7 super tampons (collection page, re-confirmed 2026-06-11; blog says 3-6; Super Leakproof No-Show Bikini PDP states 'Now absorbs about 6 super tampons')","legacy":false,"retracted":false},{"tier":"Ultra","ml_min":63,"ml_max":99,"regular_tampon_equiv_min":12.6,"regular_tampon_equiv_max":19.8,"grade":"C","source":"7-11 super tampons (collection page, re-confirmed 2026-06-11; one SKU states 'about 9 super')","legacy":false,"retracted":false}]},{"brand":"Thinx","basis":"regular tampons at THINX's own 9 mL/tampon (not the ~5 mL most brands use)","verified":"2026-09-05","tiers":[{"tier":"Light (legacy ladder)","ml_min":9,"ml_max":9,"regular_tampon_equiv_min":1.8,"regular_tampon_equiv_max":1.8,"grade":"B","source":"about 1 regular tampon (Thinx states 9 mL); the classic ladder no longer appears in current product marketing (2026-06-11) - retained to translate legacy tier names","legacy":true,"retracted":false},{"tier":"Moderate (legacy ladder)","ml_min":18,"ml_max":27,"regular_tampon_equiv_min":3.6,"regular_tampon_equiv_max":5.4,"grade":"B","source":"up to 2-3 regular tampons (legacy ladder, see Light)","legacy":true,"retracted":false},{"tier":"Heavy (legacy ladder)","ml_min":36,"ml_max":36,"regular_tampon_equiv_min":7.2,"regular_tampon_equiv_max":7.2,"grade":"B","source":"up to 4 regular tampons (legacy ladder, see Light)","legacy":true,"retracted":false},{"tier":"Super (legacy ladder)","ml_min":45,"ml_max":45,"regular_tampon_equiv_min":9,"regular_tampon_equiv_max":9,"grade":"B","source":"up to 5 regular tampons (legacy ladder, see Light)","legacy":true,"retracted":false},{"tier":"All Day","ml_min":108,"ml_max":108,"regular_tampon_equiv_min":21.6,"regular_tampon_equiv_max":21.6,"grade":"B","source":"'Absorbent layers hold up to 12 regular tampons' worth' (thinx.com/pages/how-they-work and All Day PDPs, re-verified 2026-09-05); Thinx publishes no millilitre figure for its period underwear. 108 mL is our computation, not a brand figure: 12 regular tampons at the FDA regular-absorbency ceiling of 9 g (21 CFR 801.430, greater than 6 g up to and including 9 g), which is the same 9 mL per regular tampon this table uses for Thinx's legacy ladder; the FDA floor of 6 g gives 72 mL. The 'up to 100 mL' on how-they-work is the bladder-leak line's figure (Thinx for All Leaks), stated in the FAQ answer about light bladder leaks; identical wording on the 2026-05-08 and 2026-07-03 Wayback snapshots. The 2026-06-10 verification misattributed it to the period line.","legacy":false,"retracted":false},{"tier":"All Night","ml_min":108,"ml_max":108,"regular_tampon_equiv_min":21.6,"regular_tampon_equiv_max":21.6,"grade":"B","source":"'Absorbent layers hold up to 12 regular tampons worth' (all-night PDPs, re-verified 2026-09-05) - the identical blanket claim as All Day, with no millilitre figure published and no higher overnight figure. 108 mL is our computation, not a brand figure: 12 regular tampons at the FDA regular-absorbency ceiling of 9 g (21 CFR 801.430, greater than 6 g up to and including 9 g), which is the same 9 mL per regular tampon this table uses for Thinx's legacy ladder; the FDA floor of 6 g gives 72 mL. The 'up to 100 mL' on how-they-work is the bladder-leak line's figure (Thinx for All Leaks), stated in the FAQ answer about light bladder leaks; identical wording on the 2026-05-08 and 2026-07-03 Wayback snapshots. The 2026-06-10 verification misattributed it to the period line.","legacy":false,"retracted":false},{"tier":"Overnight (Teens)","ml_min":108,"ml_max":108,"regular_tampon_equiv_min":21.6,"regular_tampon_equiv_max":21.6,"grade":"B","source":"'absorb up to 12 regular tampons (or 3 regular pads') worth of flow' (Thinx Teens PDP specs, re-verified 2026-09-05) - the same blanket claim as the adult line, with no millilitre figure published. 108 mL is our computation, not a brand figure: 12 regular tampons at the FDA regular-absorbency ceiling of 9 g (21 CFR 801.430, greater than 6 g up to and including 9 g), which is the same 9 mL per regular tampon this table uses for Thinx's legacy ladder; the FDA floor of 6 g gives 72 mL. The 'up to 100 mL' on how-they-work is the bladder-leak line's figure (Thinx for All Leaks), stated in the FAQ answer about light bladder leaks; identical wording on the 2026-05-08 and 2026-07-03 Wayback snapshots. The 2026-06-10 verification misattributed it to the period line.","legacy":false,"retracted":false}]},{"brand":"Modibodi","basis":"tampons with brand-stated mL; Modibodi states the basis itself: '(Based on 5ml tampon)'","verified":"2026-06-11","tiers":[{"tier":"Light","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"A","source":"4 tampons / up to 20 mL (US PDP re-verified 2026-06-11)","legacy":false,"retracted":false},{"tier":"Moderate","ml_min":30,"ml_max":30,"regular_tampon_equiv_min":6,"regular_tampon_equiv_max":6,"grade":"A","source":"'Moderate Absorbency: 30 mls, Tampons Equivalent: Up to 6 tampons (Based on 5ml tampon)' - US PDP verbatim, verified 2026-06-11","legacy":false,"retracted":false},{"tier":"Super","ml_min":50,"ml_max":50,"regular_tampon_equiv_min":10,"regular_tampon_equiv_max":10,"grade":"A","source":"'Super Absorbency: 50 mls, Tampons Equivalent: Up to 10 tampons (Based on 5ml tampon), Perfect For: Heaviest days and Overnight' - US PDP verbatim, verified 2026-06-11","legacy":false,"retracted":false}]},{"brand":"Saalt","basis":"tampons at ~5 mL","verified":"2026-06-11","tiers":[{"tier":"Light","ml_min":10,"ml_max":10,"regular_tampon_equiv_min":2,"regular_tampon_equiv_max":2,"grade":"B","source":"2+ light tampons","legacy":false,"retracted":false},{"tier":"Regular","ml_min":15,"ml_max":15,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":3,"grade":"B","source":"3 tampons","legacy":false,"retracted":false},{"tier":"Heavy","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"B","source":"4 tampons","legacy":false,"retracted":false},{"tier":"Super","ml_min":40,"ml_max":50,"regular_tampon_equiv_min":8,"regular_tampon_equiv_max":10,"grade":"B","source":"8+ tampons (site standard); the Leakproof Cotton Sleep Short PDP states 'replacing a full 7 pads or 10 regular tampons of flow' (verified 2026-06-11) - the range carries the brand's own spread","legacy":false,"retracted":false}]},{"brand":"Proof (Proof by Always)","basis":"regular tampons (stated directly)","verified":"2026-06-10","tiers":[{"tier":"Super-Light","ml_min":5,"ml_max":5,"regular_tampon_equiv_min":1,"regular_tampon_equiv_max":1,"grade":"B","source":"up to 1 light tampon","legacy":false,"retracted":false},{"tier":"Light","ml_min":5,"ml_max":5,"regular_tampon_equiv_min":1,"regular_tampon_equiv_max":1,"grade":"B","source":"up to 1 regular tampon","legacy":false,"retracted":false},{"tier":"Moderate","ml_min":15,"ml_max":15,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":3,"grade":"B","source":"up to 3 regular tampons","legacy":false,"retracted":false},{"tier":"Heavy","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"B","source":"up to 4 regular tampons","legacy":false,"retracted":false},{"tier":"Super-Heavy","ml_min":25,"ml_max":25,"regular_tampon_equiv_min":5,"regular_tampon_equiv_max":5,"grade":"B","source":"up to 5 regular tampons","legacy":false,"retracted":false},{"tier":"Overnight (Super Heavy Brief)","ml_min":35,"ml_max":35,"regular_tampon_equiv_min":7,"regular_tampon_equiv_max":7,"grade":"B","source":"up to 7 regular tampons","legacy":false,"retracted":false},{"tier":"Overnight (Hi-Rise / Boyshort)","ml_min":45,"ml_max":45,"regular_tampon_equiv_min":9,"regular_tampon_equiv_max":9,"grade":"B","source":"up to 9 regular tampons","legacy":false,"retracted":false}]},{"brand":"Ruby Love","basis":"single absorbency, all cuts","verified":"2026-06-05","tiers":[{"tier":"Period underwear (one level)","ml_min":12.5,"ml_max":12.5,"regular_tampon_equiv_min":2.5,"regular_tampon_equiv_max":2.5,"grade":"B","source":"2.5 tampons","legacy":false,"retracted":true}]},{"brand":"The Period Company","basis":"tampons at ~5 mL","verified":"2026-06-11","tiers":[{"tier":"Light (Thong)","ml_min":10,"ml_max":10,"regular_tampon_equiv_min":2,"regular_tampon_equiv_max":2,"grade":"B","source":"2 tampons","legacy":false,"retracted":false},{"tier":"Medium","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"B","source":"'Medium absorbency... Absorbs up to 4 tampons worth of flow!' (PDP verbatim, verified 2026-06-11)","legacy":false,"retracted":false},{"tier":"Heavy","ml_min":45,"ml_max":45,"regular_tampon_equiv_min":9,"regular_tampon_equiv_max":9,"grade":"B","source":"'Heavy absorbency... Absorbs up to 9 tampons worth of flow!' (Sleeper PDP verbatim, verified 2026-06-11; flagship styles market '10 tampons / 14 hours')","legacy":false,"retracted":false}]},{"brand":"Bambody","basis":"regular tampons at the brand's own stated 5 mL per tampon (bambody.com product pages; the Hipster Light Flow page states 'about 1 tampon-equivalent (~5 mL)')","verified":"2026-09-20","tiers":[{"tier":"Light Flow","ml_min":5,"ml_max":10,"regular_tampon_equiv_min":1,"regular_tampon_equiv_max":2,"grade":"C","source":"Hipster Light Flow only. Its product page says 'Absorbs about 1 tampon-equivalent (~5 mL)'; the same product's store-feed description says 'up to 2 tampons' worth'. The two figures disagree, so the range carries both (bambody.com, read 2026-09-20).","legacy":false,"retracted":false},{"tier":"Heavy Flow","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"B","source":"Hipster Heavy Flow product page: 'The 4-layer bamboo construction absorbs up to 4 regular tampons' worth of fluid'. The High Waist ('up to 4 tampons-equivalent') and Brief ('holds up to 4 regular tampons worth of fluid') pages state the same figure and join this row. Converted at the brand's own 5 mL per tampon (bambody.com, read 2026-09-20).","legacy":false,"retracted":false}]},{"brand":"Aisle","basis":"regular tampons with brand-stated mL","verified":"2026-06-05","tiers":[{"tier":"Essential Thong (Light)","ml_min":5,"ml_max":5,"regular_tampon_equiv_min":1,"regular_tampon_equiv_max":1,"grade":"B","source":"1 regular tampon","legacy":false,"retracted":false},{"tier":"Essential Brief/Hipster/Boxer (Moderate)","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"A","source":"4 regular tampons / ~20 mL","legacy":false,"retracted":false},{"tier":"BOOST (adjustable, +BOOSTER insert)","ml_min":20,"ml_max":40,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":8,"grade":"B","source":"4-8 regular tampons","legacy":false,"retracted":false},{"tier":"Super (Heavy / overnight)","ml_min":40,"ml_max":40,"regular_tampon_equiv_min":8,"regular_tampon_equiv_max":8,"grade":"A","source":"8 regular tampons / ~40 mL","legacy":false,"retracted":false}]},{"brand":"WUKA","basis":"brand-stated mL","verified":"2026-06-10","tiers":[{"tier":"Light","ml_min":7,"ml_max":7,"regular_tampon_equiv_min":1.4,"regular_tampon_equiv_max":1.4,"grade":"C","source":">=7 mL (light-tier claim NOT first-party confirmed)","legacy":false,"retracted":false},{"tier":"Medium","ml_min":15,"ml_max":15,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":3,"grade":"A","source":"up to 15 mL (~3 tampons)","legacy":false,"retracted":false},{"tier":"Heavy","ml_min":20,"ml_max":20,"regular_tampon_equiv_min":4,"regular_tampon_equiv_max":4,"grade":"A","source":">=20 mL","legacy":false,"retracted":false},{"tier":"Super Heavy","ml_min":60,"ml_max":60,"regular_tampon_equiv_min":12,"regular_tampon_equiv_max":12,"grade":"A","source":"holds up to 60 mL, 'equivalent to 12 tampons' worth' (re-confirmed on wukawear.com 2026-06-10)","legacy":false,"retracted":false}]},{"brand":"Rael","basis":"regular tampons (conflicting claims)","verified":"2026-06-05","tiers":[{"tier":"Reusable Boyshort","ml_min":15,"ml_max":25,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":5,"grade":"C","source":"3-5 regular tampons (page: 4-5; blog: 3)","legacy":false,"retracted":false}]},{"brand":"Hanky Panky","basis":"regular tampons at ~5 mL","verified":"2026-06-11","tiers":[{"tier":"Light","ml_min":10,"ml_max":10,"regular_tampon_equiv_min":2,"regular_tampon_equiv_max":2,"grade":"B","source":"'Light Absorbency: absorbs up to 2 panty liners or 2 regular tampons of leakage' (leakproof thong PDP, verified 2026-06-11)","legacy":false,"retracted":false},{"tier":"Regular","ml_min":15,"ml_max":15,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":3,"grade":"B","source":"'Regular Absorbency: absorbs up to 3 panty liners or 3 regular tampons of leakage' (boyshort / French brief / V-kini PDPs, verified 2026-06-11)","legacy":false,"retracted":false}]},{"brand":"Skims","basis":"tampons at ~5 mL (brand product copy)","verified":"2026-06-10","tiers":[{"tier":"Period Panties Thong","ml_min":10,"ml_max":10,"regular_tampon_equiv_min":2,"regular_tampon_equiv_max":2,"grade":"B","source":"three-layer gusset 'absorbs up to 2 tampons worth' (brand product copy; the static product page hides the description, so verified via search-indexed skims.com copy)","legacy":false,"retracted":false},{"tier":"Period Panties Brief","ml_min":15,"ml_max":15,"regular_tampon_equiv_min":3,"regular_tampon_equiv_max":3,"grade":"B","source":"three-layer gusset 'absorbs up to 3 tampons worth' (brand product copy, same caveat)","legacy":false,"retracted":false}]}]}