Hoodie GSM: Compare Fabric Weight, Fleece and Fit

What 400 GSM actually means

One square metre of 400 GSM fabric has a mass of 400 grams. A square metre of 300 GSM fabric weighs 100 grams less. That is a comparison of equal areas, not a prediction of the complete garments’ weights. The fabric area used, hood layers, pockets and other components still matter.

Printful gives the conversion factor of approximately 33.91 between ounces per square yard and GSM. Divide GSM by 33.91 to get oz/yd²: 300 GSM is about 8.85 oz/yd²; 400 GSM is about 11.80 oz/yd². This is an area-based unit conversion. Converting 400 grams directly to ounces would give the wrong fabric-weight comparison.

Real published hoodies with different specifications

AS Colour’s September 2023 manufacturer guide describes these reference styles. They are published design examples, not a promise that today’s stock, colours or every later version is identical.

The most useful comparison is between the two 350 GSM examples. Their stated fabric weights match, but the interior construction and sleeve designs differ. Someone choosing only by the number would miss information that the manufacturer itself uses to distinguish the styles.

The 400 GSM example also changes the cut to oversized. If it appears roomier in a photograph, weight alone cannot explain that difference. Separate a fabric preference from a silhouette preference before choosing a listing.

French terry and brushed fleece are not synonyms

CottonWorks explains French terry as an un-napped knit with loops on the reverse. Brushing or napping the interior yarns produces the fleecy surface associated with fleece. It also notes that fleece can be made from cotton, cotton blends or synthetic fibres. Construction and composition therefore describe different things.

Ask for a clear view of the inside if the listing does not identify it. Visible loops and a brushed surface answer a question that a front-view photograph cannot. A cotton percentage alone does not tell you which interior you will get.

How much heavier is a 400 GSM hoodie than a 300 GSM hoodie?

For the same fabric area, 400 GSM is one-third heavier than 300 GSM: 400 ÷ 300 is approximately 1.33. It does not follow that two finished hoodies will differ by one-third. Their sizes, cuts, layers and components may be different.

If finished weight matters, request the item’s measured weight in the intended size. For shipping, packaging is another separate measurement. Do not place “400 g” in a garment-weight column because a listing says 400 GSM.

A practical way to choose a hoodie specification

• For an under-jacket layer, compare the garment’s actual bulk, sleeve cut and dimensions alongside GSM.
• For a substantial standalone silhouette, inspect body cut, ribbing and hood structure; a high number alone does not establish the shape.
• For a particular interior feel, identify French terry or brushed fleece rather than guessing from cotton content.
• For delivery planning, keep fabric GSM, measured garment weight and packed parcel weight in separate fields.

These are comparison criteria, not universal temperature ratings. Climate, activity, layering and personal preference change what feels suitable. None of the cited specifications provides a laboratory warmth result for an unrelated seller’s item.

What belongs in the spreadsheet row

Keep the stated GSM, fibre composition, inside finish, cut and any verified garment measurement. If the GSM applies only to the main body fabric, retain that qualification. A note such as “350 GSM, French terry, regular fit; composition and size chart confirmed” conveys more than “heavyweight premium.”

Before buying, compare those claims with the actual source listing. The AS Colour examples demonstrate how to read specifications; they do not authenticate another product or make every hoodie carrying a similar name equivalent.