How to Choose Suit Size Online

Start with fresh measurements, not memory

Online shopping removes the fitting room, so your measurements have to do the work that trying on used to do. Measure yourself again before you order, even if you bought a suit last year, because weight and shape change slowly and memory rounds the numbers in the wrong direction. Take the chest, trouser waist, shoulder width, sleeve length, jacket length and trouser inseam with a soft tape, and write them down together.

Do not order from the size you wore last time without checking it. A size letter from one brand is not the same as a size letter from another, and a number size from a suit you bought years ago may sit in a different row now. Fresh numbers take ten minutes and save a return, so treat them as the first step of the order, not as an optional extra.

Read the brand chart row by row

Open the brand chart for the suit you are buying and compare your numbers with the full row, not just the size letter. Find the row where your chest falls, then check your trouser waist, shoulder width, sleeve length, jacket length and inseam against that same row. If most of your numbers sit in one row and one number sits in another, note which one it is, because that is the measurement most likely to cause trouble.

Pay close attention to the shoulder width and the sleeve length, because those two are the hardest to fix after the suit arrives. A chest that fits means little if the shoulders droop or the sleeves cover your hands. If the brand lists garment measurements rather than body measurements, compare your numbers with the garment numbers and allow a little ease, because a garment chest is always larger than the body chest it is cut for.

Fit notes and fabric notes matter

Read the fit notes as well as the chart. A brand that describes a suit as fitted has already built a close cut into its sizes, so sizing down on top of that can leave you with a jacket that pulls at the button and strains across the chest. A brand that describes a suit as relaxed has built ease into the same size letter, so the same letter will feel looser. Match the fit note to the look you want, then pick the size from your measurements.

Fabric notes matter too, because cloth changes how a size feels. A firm wool holds its shape and shows a tight fit clearly, while a stretch blend forgives a little tightness and a soft unstructured cloth drapes loosely even in the right size. Linen and cotton crease and relax with wear, so a suit in those cloths may feel closer on the first wear than after a day of wearing. Read both notes before you decide between two sizes.

Photos and reviews can help, with limits

Model photos show how a suit is meant to look, but the model is not you, so use the photos for the shape of the suit rather than for the size. Look at where the jacket hem falls on the model, how much cuff shows, and how the trousers break at the shoe, and compare those proportions with your own height and build. A photo of a tall model in a regular length will not tell you how the same length falls on a shorter frame.

Customer reviews can add useful detail, especially when several reviewers mention the same point, such as sleeves running long or shoulders running narrow. Treat one review as an opinion and several reviews saying the same thing as a pattern. Reviews that mention the reviewer's height, chest and the size they bought are the most useful, because you can compare their numbers with yours.

Returns and exchanges: plan before you order

• Check the returns window and whether returns are free before you order, not after the suit arrives.
• Keep the tags on and try the suit on at home over a shirt, so it can go back in the same condition.
• Try both the jacket and the trousers together, because a suit is judged as a pair.
• Walk, sit and raise your arms during the home try on, and check the fit in a mirror from the front, side and back.
• If the size is wrong, exchange it promptly rather than keeping a suit that does not fit.

A short ordering checklist

Before you press buy, run through the list once more. Fresh measurements taken, starting size from the calculator, brand chart row compared across all seven numbers, fit note read, fabric note read, length letter checked against your height and jacket length, and returns policy understood. If any of those is missing, fill the gap first. A suit ordered with all of them checked is far more likely to fit on the first try.

When the suit arrives, judge it as a pair and give yourself time. Put the jacket and trousers on together, stand in front of a mirror, and move through the checks in this guide. If it fits, keep it. If it does not, use what you learned from the try on to pick the next size, and note the change for the next order from the same brand.