What Does 400 GSM Mean on a Hoodie?

GSM is fabric weight per area, not hoodie weight

GSM stands for grams per square meter. AS Colour explains that fabric weight is the mass of a sample divided by its area. A 400 GSM fabric is heavier per unit of area than a 300 GSM fabric. It does not mean the whole hoodie weighs 400 grams.

A finished hoodie includes a body, sleeves, hood, ribbing, seams and perhaps drawcords or a zipper. Larger sizes use more material, so total garment weight varies even at the same GSM. If a product page says “400 g” without an area unit, ask whether it means fabric GSM or total weight.

Is 400 GSM heavy for a hoodie?

It is substantial compared with lighter sweatshirt fabrics, but “heavyweight” is not a universal quality grade. AS Colour lists hoodies at 290, 320 and 350 GSM and calls its 400 GSM Heavy Hood “ultra heavyweight” within that range. That is one brand’s positioning, not an industry rule.

Extra fabric mass may create a denser, more structured drape. Cut changes the effect: a wide, cropped hoodie can hang differently from a long, fitted one at the same GSM. For a specific silhouette, check garment dimensions. GSM cannot tell you shoulder shape, body length or how the hood sits.

Why 400 GSM French terry and fleece can feel different

GSM does not tell you whether the inside is looped or brushed. CottonWorks explains that French terry has reverse-side loops, while fleece has a brushed or napped interior. AS Colour lists both a French terry hoodie and a fleece hoodie at 350 GSM. The same weight can have a different surface.

That difference affects feel against a T-shirt and may influence seasonal use. Neither construction is automatically better. If a listing shows only the smooth exterior, request a close view of the inside or a precise fabric description. A front thumbnail cannot distinguish brushed fleece from unbrushed loops.

What a high GSM number cannot prove

A 400 GSM claim does not establish softness, shape retention, low pilling or reliable stitching. Yarn, fiber mix, knit structure, finishing and care influence how a sweatshirt wears. CottonWorks shows that knit structures differ in stability and texture. GSM measures one property, not the entire product.

A higher number also cannot provide a universal temperature recommendation. A brushed interior, loose neckline and what you wear underneath affect comfort. If warmth is your priority, ask about interior construction and fabric composition instead of assuming every 400 GSM hoodie suits the same weather.

How to compare two hoodies with different GSM claims

First confirm that both numbers describe the main body fabric. A seller might quote trim, lining or total garment weight instead. Then compare fiber percentages, inside finish, hood construction and care guidance. Between 400 and 350 GSM, the 50 GSM gap measures fabric mass per square meter; it cannot decide which hoodie feels better.

Use measurements and photos for design details GSM cannot cover. Heavier fabric may suit a boxy silhouette; a lighter layer may fit beneath a jacket more easily. Compare the same intended size and color, and note which claims have evidence. “Heavy hoodie” alone leaves a large information gap.

• Confirm the unit: GSM or g/m² for fabric, grams or ounces for a finished garment.
• Check fiber mix and whether the inside is loopback French terry or brushed fleece.
• Compare cut, hood, cuffs and care information separately from the weight number.

What if the product listing does not state GSM?

Ask the seller for the main fabric’s GSM and fiber composition. A label photo or manufacturer specification beats a thumbnail-based guess. In the United States, the FTC says most textile products must carry fiber-content information and care instructions; those are separate from a marketed GSM claim. Label rules vary by market.

This iTaoBuy Spreadsheet-style directory does not measure fabric or certify seller descriptions. Its cards help you find styles, but missing GSM remains unknown until the full listing or seller supplies it. Without a reliable specification, compare disclosed materials and design; do not read “heavyweight” as a measured 400 GSM.