The Peter Pan collar midi dress pairs a two-column, double-breasted-looking bodice with a self-tie waist sash and a pleated skirt. Its red gallery makes the contrasting collar and button placement easy to see. The first buying decision is whether the upper dress has enough room before the sash changes its outline. The listing gives shoulder, chest, waist and length for S, M and L, but does not explain how the buttons fasten or how the waist was measured.

Start with a dress that closes comfortably

Lay a button-front or similarly structured dress you own flat. Record shoulder width, chest circumference and waist circumference at consistent points; compare it with the seller’s measurement method rather than assuming a body measurement is a garment measurement. If you plan a blouse underneath, use the reference dress with that same underlayer. The product photo shows a red version over the model, but does not establish the room available for your own layer.

Read the actual changes between sizes

S lists 14 in across shoulders, 35 in chest, 34 in waist and 41 in length. M lists 14.5, 36.5, 35.5 and 41 in. The move from S to M adds half an inch at the shoulders and 1.5 in at both chest and waist, while the published length stays the same. L lists 15, 38, 37 and 41 in. If your reference dress is comfortable at roughly M’s chest and shoulder figures, the sash is a styling decision, not a reason to assume that S’s smaller bodice will close comfortably. The source does not label the figures as body or garment dimensions, so confirm that before treating the comparison as a fit recommendation.

Then decide how you want the sash to sit

Try your reference dress with a removable belt or scarf tied loosely, then closer, at the natural waist. This shows your preferred outline while leaving the chest and shoulder fit unchanged. On the listed dress, confirm whether the sash is separate or fixed, where it is anchored, and whether the waist figure was taken before or after tying. The picture cannot answer those construction questions. The source calls the bodice double-breasted, but it does not establish whether both button columns are functional or one is decorative; ask for an open-front photo if fastening access matters.

Red, Brown and Black are the active color choices on the product page. Choose the color you want after checking the bodice dimensions, then use the sash to plan the silhouette. The listed 41 in length is the same for all three sizes, but its measuring origin is unstated; request that point if hem placement is important.