Guides
Short, data-backed reads. Best-of picks come from the live catalog ranked by verified capacity; every number traces to a brand's published claim or a named primary source - the same discipline as the data table.
Explainer
How much do period underwear actually hold?
Brand claims run about 20 to 100 mL. The only lab test with real blood measured about 1 to 3 mL before leaking. Both are true - they answer different questions. Here is how to use each.
Updated 2026-06-12
Explainer
How many tampons is Knix Heavy?
Knix counts in SUPER tampons, not regular ones. Its Heavy tier is about 4 to 7 super tampons, which works out to roughly 36 to 63 mL - more than the same number of regular tampons would suggest.
Updated 2026-06-12
Explainer
Is Thinx Super 100 ml?
Short answer: that question mixes two different Thinx numbers. Thinx dropped its old per-tier ladder; its current styles print one blanket "up to 100 mL" claim. Here is what is actually published, verified on the brand's pages.
Updated 2026-06-12
Bladder Leak
Period underwear vs. incontinence underwear: what's the difference?
They look alike and some brands sell crossover styles, but period and incontinence underwear are tuned for different fluids and labeled on different scales. When one product serves both, and when it does not.
Updated 2026-06-12
Bladder Leak
Reusable vs. disposable incontinence underwear
Washable reusable underwear versus disposable pads and pull-ups for bladder leaks: cost over time, capacity, comfort, and dignity - and exactly where each one wins.
Updated 2026-06-12
Bladder Leak
Best washable incontinence underwear for women
Reusable, washable incontinence underwear for light bladder leaks - the in-stock styles in our catalog, and an honest note on where this young category is still thin.
Updated 2026-06-12
Explainer
How many pairs of period underwear do you need?
A full cycle usually takes six to nine pairs, depending on your flow, how often you change, and your laundry routine. How to work out your own number without over-buying.
Updated 2026-06-12
Explainer
Are period underwear worth it?
The honest cost case: a higher upfront price that pays back over about two years versus disposables - if you get the absorbency right the first time. The math, and the one trap to avoid.
Updated 2026-06-12
Comparison
Period underwear vs. pads and tampons
How period underwear compares to pads and tampons on absorbency, comfort, cost over time, and convenience - and where each still wins. No brand's thumb on the scale.
Updated 2026-06-12
How It Works
Do period underwear actually work?
Yes, within their capacity - and the honest version of that answer is the useful one. What the independent lab data shows, where they work best, and the trick to getting them right the first time.
Updated 2026-06-12
How It Works
How does period underwear work?
Period underwear works through layers: a wicking top layer, an absorbent core that holds the liquid, and usually a leak-resistant barrier. What each does, and why the claimed capacity is a lab maximum.
Updated 2026-06-12
Care
How long does period underwear last?
Most brands estimate around two years or 40-plus washes with proper care. What shortens that, and the signs a pair has lost its absorbency and needs replacing.
Updated 2026-06-12
Care
How to wash period underwear
Rinse cold, wash cold on gentle, skip the fabric softener, air dry. The simple routine that keeps the absorbent layer working - and the two mistakes that wreck it fastest.
Updated 2026-06-12
Best Of
Best period underwear for teens and first periods
How to choose period underwear for a teen or a first period: which absorbency tier to start with, how sizing works, and the teen-specific styles in our catalog.
Updated 2026-06-12
Best Of
Best postpartum period underwear (reusable)
Reusable, high-capacity period underwear for postpartum bleeding (lochia), ranked by verified millilitres. How reusable pairs differ from the disposable mesh underwear hospitals provide.
Updated 2026-06-12
Best Of
Best period underwear for light days and spotting
For light days, spotting, the end of a period, or daily discharge you want a thinner, lower-capacity pair. These are the period underwear with a verified capacity of about 20 mL or less.
Updated 2026-06-12
Best Of
Best overnight period underwear
Overnight wear needs the highest capacity and the most coverage. These are the period underwear with a verified capacity of 60 mL or more, ranked by how much they hold.
Updated 2026-06-12
Best Of
Best period underwear for heavy flow
The most absorbent period underwear for heavy flow, ranked by verified capacity in millilitres - not by the word "Heavy," which means anywhere from 20 to 63 mL depending on the brand.
Updated 2026-06-12
Explainer
Why "12 tampons' worth" means 60 mL at one brand and 100 mL at another
Two brands use the identical phrase for a 67% different capacity. The receipts, the missing standard behind them, and how to compare honestly.
Updated 2026-06-11
Explainer
What AI gets wrong about period underwear absorbency
Five measurable failure modes - invented tampon math, marketing tags read as tiers, stale brand ladders, same-word-different-number tiers, claims quoted as lab facts - and the 5-question audit that catches them.
Updated 2026-06-11
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