How far each brand's chart reaches
From the size charts we hold and re-verify: Ruby Love's chart runs to 8XL (a US 32), Modibodi's to a 22 (its 6XL), WUKA's to 6XL, Aisle's to 5X, Saalt's to 4XL, Thinx's to 4X, and Knix's to XXXXL, which is its 4X. Proof stops at 3XL and Hanky Panky at XL. The Period Company's store lists sizes to 6X, though we hold no verified chart for it yet. The size hub prints every chart with the hip measurement each size covers, so you can see where your hips fall at each brand before you shop. A chart that reaches 8XL is not automatically the right one; the right one is the brand whose chart puts your hips inside a size, in a tier that covers your flow.
Size from the hip, and expect the brands to disagree
Period underwear is sized on a hip measurement, around the fullest part of the hips and seat, and each brand draws its size boundaries differently. That disagreement is larger at the top of the range, where one brand's 3X can cover the hips another brand calls 4X. The size finder takes one hip measurement and returns your size at every charted brand, computed in your browser. Use it before trusting the size you wear elsewhere, and if you land between sizes, go up for a snug seal at the leg rather than down.
Fit points that matter more at larger sizes
Two things come up more often in larger sizes. First, the gusset needs to be long enough front to back: flow runs backward when you sit or lie down, and a panel cut for a smaller frame can end short of where it needs to be. High-waisted styles and briefs carry the longest panels. Second, leg elastic matters: a leg opening that digs in will leak at the edge and roll, while one that gaps will leak outright. Brands that offer a bonded or wide-band leg edge tend to sit flatter. Neither of these is a capacity issue, so a pair that leaks in a larger size is often a fit issue before it is a tier issue; the leaking guide separates the two.
Stock is the real constraint
Extended sizes sell out first and restock last, which is why this page checks the sizes in stock at the last scrape rather than the sizes a brand prints on its chart. A pair that appears here was in stock in a 3X-or-larger size at the last refresh. If the list is short, that is stock, not a judgment about the pairs, and the size hub still shows every brand's full range.
Quick answers
- What period underwear brands go up to 4X or 5X?
- From the charts we hold: Ruby Love runs to 8XL, Modibodi to a 22 (its 6XL), WUKA to 6XL, Aisle to 5X, Saalt to 4XL, Thinx to 4X, and Knix to XXXXL (its 4X). The size hub prints each chart with hip measurements, and the list above shows which of those pairs are in stock right now in a 3X or larger size.
- Is plus-size period underwear sized the same as regular sizes?
- It is sized the same way - from a hip measurement - but the brands draw their boundaries differently, and the disagreement widens at the top of the range. Measure your hips and use the size finder to see each brand's answer, rather than assuming your usual 3X carries across.
- Does plus-size period underwear hold more?
- Not by size. Capacity is set by the tier (Light, Heavy, Overnight and so on), not the size, though a larger pair carries a physically larger panel of the same construction. Choose the tier from your flow in millilitres with the translator, then choose the size from your hips.
- Why does my plus-size period underwear leak at the legs?
- Usually fit, not capacity: a leg opening that gaps lets flow escape before the panel absorbs it, and one that digs in rolls and leaks at the edge. Check your hip measurement against that brand's chart, size up if you are between sizes, and favor styles with a wide or bonded leg edge. The leaking guide walks through all five causes in order.
Related guides
What size period underwear should I get?
Period underwear is sized on your hip measurement, not your usual dress or bra size, and brands disagree, so the same body can be a M at one brand and an L at another. How to get it right the first time.
Best high-waisted period underwear
High-waisted period underwear ranked by verified capacity in millilitres. The higher back rise is not just tummy coverage - it is where the absorbent layer needs to reach for overnight and heavy days.
Why is my period underwear leaking? 5 causes and the fix for each
Leaking is almost always one of five things: the wrong absorbency for your flow, the fit at the legs, wearing it past capacity, dead wicking, or too low a rise. How to tell which, and the fix.
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.
Your size at every brand, from one measurement
Measure your hips once. The size finder returns your size at every charted brand, and the size hub shows each brand's full chart.