Size guide
How U2SKIIN sizing runs, what a pair size like L/XL means on a robe, and the two measurements that settle it.
The two numbers
Measure a garment you already own, laid flat, and compare numbers to numbers. Chest seam to seam and doubled decides a top. Waistband flat and doubled decides a bottom. Body measurements taken at home move by an inch depending on the tape and the breath. A garment on a table does not move.
Which way to lean
Knit gives and springs back, so take the smaller size. Woven cotton does not give at all, so take the larger one. Fleece adds bulk without stretching, so take your usual size. On any bottom the waistband forgives and the rise does not, and that is the reason we say size down on bottoms unless the fabric is fleece.
Paired sizes
Several robes and onesies are graded in pairs, S/M and L/XL and upward. That is not a shortage. A garment that wraps is adjusted by its tie, so one step honestly covers two. On the line between two pairs, take the larger: a robe that meets exactly at the front keeps opening.
The ladder on each page
Every product page carries a row of the sizes that exist in that colour and carry a price today. A missing step means the size is not made in that colour or has no current price. It does not mean it is coming, and switching colour can change the whole row.
Washing is part of sizing
Cold water and low heat keep a piece the size you bought. Hot water and a hot dryer take a cotton set down most of a size, unevenly, so the top comes back short in the body while staying wide across the chest. Buying a size up to allow for it is planning for a wash you do not have to do.
The long version, with tables and the measurements written out, is in the journal: sizing sleepwear you will never try on.