Are period underwear sizes the same as regular underwear?

No. Period underwear is sized on your hip measurement, and every brand draws its own chart, so your usual underwear or dress size is only a guess. The same 44-inch hip is a Large at Saalt, an XL at Thinx, and a 2XL at WUKA - all read from the brands' own published charts.

What if I am between sizes in period underwear?

Size up. A snug-but-not-tight fit seals better against leaks, while a pair that digs in can wick at the edges. Several brands say it themselves: Aisle and Rael both recommend sizing up when in doubt.

Which period underwear brands run small?

By the brands' own guidance and the consistent reviews in our chart data: Knix, Aisle, Rael, and Bambody run small or advise sizing up. Thinx, Ruby Love, and The Period Company say true to size outright, and Hanky Panky presents its fit as true-to-size stretch. Saalt, Proof, Modibodi, and WUKA publish no direction either way - go with your chart match. Each brand's note sits under its chart on this page.

How do I measure my hips for period underwear?

Wrap a soft measuring tape around the fullest part of your hips and seat, level with the floor, and read the number in inches. That single measurement is what every brand's chart keys on - waist is secondary where it is published at all.

Period underwear size charts, every brand on one page

Every brand draws its own size chart, so the same hips land in a different size at different brands - and no brand will show you the others' charts. Here they all are: each brand's own published hip-to-size table, with its runs-small or runs-large note.

From each brand's own published chart · Updated 2026-06-05

One measurement reads every chart

Take a soft tape around the fullest part of your hips and seat, level with the floor. That one number is what every chart below keys on. Or let the size finder read them all for you - it returns your size at every brand at once, computed in your browser. Wondering whether they run small in general? The sizing guide answers that.

Every brand's chart at a glance

All ranges in inches, straight from each brand's own chart. Compare any two brands and you will see why “I'm usually a Medium” misfires: the same 44-inch hip is a Large at Saalt, an XL at Thinx, and a 2XL at WUKA.

Knix

See Knix

Runs small - size up if you are between sizes.

Size	Waist (in)	Hip (in)
S	23-27	33-37
M	28-31	38-41
L	32-34	42-44
XL	35-37	45-47
XXL (2X)	38-40	48-50
XXXL (3X)	not published	51-53
XXXXL (4X)	not published	54-56

From Knix's own published chart · checked 2026-06-05

Thinx

See Thinx

Presented as true to size by the brand.

Size	Waist (in)	Hip (in)
XS	25-26	35-36
S	27-28	37-38
M	29-30	39-40
L	31-32	41-42
XL	33-34.5	43-44.5
X (plus)	36-37	43-44
1X	38-40	45-47
2X	42-44	49-51
3X	46-48	53-55
4X	50-52	57-59

From Thinx's own published chart · checked 2026-06-05 · not fully re-verified at source

Modibodi

See Modibodi

The brand publishes no sizing direction - order your usual size.

Size	Waist (in)	Hip (in)
0/XXXS	21-22	31-32
2/XXS	23-24	33-34
4/XS	25-26	35-36
6/S	27-28	37-38
8/M	29-30	39-40
10/L	31-32	41-42
12/XL	33-34	43-44
14/2XL	35-36	45-46
16/3XL	37-38	47-48
18/4XL	39-40	49-50
20/5XL	41-42	51-52
22/6XL	43-44	53-54

From Modibodi's own published chart · checked 2026-06-05

Saalt

See Saalt

No runs-small or runs-large signal in our data - order your usual size.

Size	Waist (in)	Hip (in)
XXS	23	29-30
XS	24-25	30-33
S	26-27	33-37
M	27.5-29	38-40
L	29.5-31.5	41-44
XL	32.5-34.5	45-46
2XL	35.5-38	47-50
3XL	39-43	51-54
4XL	44-48	55-58

From Saalt's own published chart · checked 2026-06-05

Proof (Proof by Always)

See Proof (Proof by Always)

No runs-small or runs-large signal in our data - order your usual size.

Size	Waist (in)	Hip (in)
XS	23-25	33-35
S	25-28	35-38
M	28-31	38-41
L	31-34	41-44
XL	34-37	44-47
2XL	37-40	47-50
3XL	40-44	50-54

From Proof (Proof by Always)'s own published chart · checked 2026-06-05

Ruby Love

See Ruby Love

Presented as true to size by the brand.

Size	Waist (in)	Hip (in)
XXS (US 0)	22-24	33-34
XS (US 2)	25-26	35-36
S (US 4/6)	27-28	37-38
M (US 8)	29-30	39-40
L (US 10-12)	31-32	41-42
XL/1X (US 14-16)	33-34.5	43-44.5
2XL (US 20)	35-37	45-47.5
3XL (US 22)	37.5-38.5	48-49.5
4XL (US 24)	39-40.5	50-51
5XL (US 26)	41-42.5	51.5-53
6XL (US 28)	43-44.5	54-55
7XL (US 30)	45-46.5	56-57
8XL (US 32)	47-48.5	58-59

From Ruby Love's own published chart · checked 2026-06-05

Aisle

See Aisle

Runs small - size up if you are between sizes.

Size	Hip (in)
XXS	33-34
XS	35-36
S	37-38
M	39-40
L	41-42
XL	43-44
1X	44-46
2X	48-50
3X	52-54
4X	56-58
5X	60-62

From Aisle's own published chart · checked 2026-06-05

WUKA

See WUKA

The brand publishes no sizing direction - order your usual size.

Size	Hip (in)
XXS	31.5-33.5
XS	33.5-35.4
S	35.4-37.4
M	37.4-39.4
L	39.4-41.3
XL	41.3-43.3
2XL	43.3-45.3
3XL	45.3-47.2
4XL	47.2-49.2
5XL	49.2-51.2
6XL	51.2-53.1

From WUKA's own published chart · checked 2026-06-05

Rael

See Rael

Runs small - size up if you are between sizes.

Size	Waist (in)	Hip (in)
Small (reusable, numeric 0-2)	24-26	34-36
Medium (reusable, numeric 2-4)	26-28	36-38
Large (reusable, numeric 4-8)	28-31	38-40
X-Large (reusable, numeric 8-10)	31-33	40-42
XX-Large (reusable, numeric 10-16)	33-37	42-44

From Rael's own published chart · checked 2026-06-05

Hanky Panky

See Hanky Panky

No runs-small or runs-large signal in our data - order your usual size.

Size	Waist (in)	Hip (in)
XS	24-25	34-35
S	26-27	36-37
M	28-29	38-39
L	30-33	40-43
XL	34-37	44-46

From Hanky Panky's own published chart · checked 2026-06-05

Brands that publish no numeric chart

The Period Company: Presented as true to size by the brand. No hip-to-size table is published, so the size finder cannot compute a size for this brand - order by its own size guidance.
Bambody: Runs small - size up if you are between sizes. No hip-to-size table is published, so the size finder cannot compute a size for this brand - order by its own size guidance.

Or start from your hip measurement

One page per hip measurement, showing your size at every brand at once.

Quick answers

Are period underwear sizes the same as regular underwear?: No. Period underwear is sized on your hip measurement, and every brand draws its own chart, so your usual underwear or dress size is only a guess. The same 44-inch hip is a Large at Saalt, an XL at Thinx, and a 2XL at WUKA - all read from the brands' own published charts.
What if I am between sizes in period underwear?: Size up. A snug-but-not-tight fit seals better against leaks, while a pair that digs in can wick at the edges. Several brands say it themselves: Aisle and Rael both recommend sizing up when in doubt.
Which period underwear brands run small?: By the brands' own guidance and the consistent reviews in our chart data: Knix, Aisle, Rael, and Bambody run small or advise sizing up. Thinx, Ruby Love, and The Period Company say true to size outright, and Hanky Panky presents its fit as true-to-size stretch. Saalt, Proof, Modibodi, and WUKA publish no direction either way - go with your chart match. Each brand's note sits under its chart on this page.
How do I measure my hips for period underwear?: Wrap a soft measuring tape around the fullest part of your hips and seat, level with the floor, and read the number in inches. That single measurement is what every brand's chart keys on - waist is secondary where it is published at all.

Get the exact answer for your measurement

One hip measurement returns your size at every brand at once, with the runs-small and runs-large notes built in - computed in your browser, never sent anywhere.

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