Buying nightwear online without trying it on can feel like a gamble, but most fit problems come down to three things: the cut around the shoulders, the flare below the waist and the fabric weight. Get those right and the size label matters far less.
Start with the shoulder and bust
If a nighty pulls across the chest or gapes at the armhole, no amount of length or print will make it comfortable to sleep in. Look for a raglan or set-in sleeve with a little ease - not tight, not baggy - and check the neckline sits flat against the collarbone rather than sliding off one shoulder.
Let the flare do the work
A woman with a fuller hip and thigh will usually feel most comfortable in an A-line or umbrella-cut maxi that skims rather than clings from the waist down. Straight-cut nighties suit a straighter frame, while a gathered empire waist is forgiving for almost every body type because it skips the waistline altogether.
Fabric changes the fit
The exact same pattern can feel completely different in cotton versus a cotton-lycra blend. A little stretch in the fabric means you can comfortably size down for a neater silhouette, while pure cotton or rayon, which does not stretch, is safer sized true-to-chart or slightly up if you prefer a looser sleep fit.
Our rule of thumb
When in between two sizes, size up for the bust and hip measurement rather than the label you normally wear in daywear - nightwear is meant to move with you through the night, not hold you in.