400gsm vs 300gsm Hoodie: What's the Difference?
A 400gsm hoodie is denser, heavier, and more structured than a 300gsm hoodie. The difference is not subtle — it is a different category of garment. This guide explains what GSM measures, how it affects construction and drape, and which weight is the right choice for UK autumn and winter wear. For the full context on heavyweight cotton basics, see our complete guide to heavyweight cotton basics.
What is GSM and what does it measure?
GSM stands for grams per square metre. It is the standard measurement of fabric density — how much yarn is packed into each square metre of fabric. A higher GSM means more yarn per unit area: a denser knit, a heavier hand-feel, and a more substantial garment overall.
GSM is not the same as thickness, though the two are related. A 400gsm loop-back fleece is denser and heavier than a 300gsm loop-back fleece of the same construction — but the difference is in the yarn density and loop count, not just the physical thickness of the fabric. According to the Textile Institute, fabric weight is one of the primary determinants of thermal performance and structural integrity in knitted fleece garments — higher GSM correlates directly with improved insulation and resistance to deformation under repeated wear.
300gsm vs 400gsm: the real difference
300gsm is a mid-weight fleece. It is comfortable in mild autumn conditions, lighter in hand, and more breathable. The fabric drapes loosely — it follows the body rather than holding a shape. It is the correct choice for layering under a jacket or for transitional weather. Most high-street hoodies sit at 280–320gsm.
400gsm is a heavyweight fleece. The fabric has a drop weight — it falls with authority and holds a silhouette independently. It is warm enough to replace a light jacket in UK autumn and winter conditions. The denser construction resists pilling and surface degradation significantly better than 300gsm alternatives. It is not a layering piece — it is the outer layer. For a full breakdown of how loop-back fleece is constructed at this weight, see our guide to what is loop-back fleece.
The practical test: hold a 300gsm hoodie and a 400gsm hoodie by the hood and let them hang. The 400gsm falls straight and holds its shape. The 300gsm collapses and folds. That difference in behaviour is the GSM difference made physical.
Drape, structure, and silhouette
At 300gsm, a hoodie drapes. At 400gsm, a hoodie stands. The distinction matters for silhouette — a 400gsm dropped-shoulder hoodie holds its shape across the shoulder and chest, creating a clean, structured line. A 300gsm version of the same cut will collapse at the shoulder and lose the silhouette within a few hours of wear.
For oversized or dropped-shoulder cuts specifically, fabric weight is not optional — it is structural. The silhouette only works if the fabric is heavy enough to hold it. This is why premium heavyweight hoodies are cut with a dropped shoulder: the weight of the fabric does the work that tailoring would otherwise require.
Warmth and durability
A 400gsm loop-back fleece traps more air in its interior loops than a 300gsm equivalent — more loops per square metre means more insulation. For UK conditions from September through March, 400gsm is the functional threshold for wearing a hoodie as an outer layer without a jacket.
Durability follows the same logic. A denser fabric has more yarn to absorb the friction and stress of repeated wear and washing. Surface pilling — the primary failure mode of cheaper fleece — occurs when surface fibres break free and tangle. At 400gsm with ring-spun cotton, the yarn is tighter and the surface fibres are fewer. The garment looks the same after 50 washes as it did after five. For the correct care method, see our guide to how to wash a heavyweight cotton hoodie.
Which weight should you choose?
Choose 300gsm if: you want a lighter layer for mild conditions, you plan to wear it under a jacket, or you prioritise breathability over warmth and structure.
Choose 400gsm if: you want a hoodie that functions as an outer layer in UK autumn and winter, holds a silhouette, and lasts significantly longer than a standard high-street option. If you are buying one hoodie and want it to last, 400gsm is the correct choice.
echelonn. aegis. — 400gsm loop-back fleece
The aegis. is built at 400gsm loop-back fleece, 100% ring-spun cotton. Dropped shoulder. Structured hood. Kangaroo pocket. Ribbed cuffs and hem. Tonal four-bar mark embroidered on the left chest — same colour as the garment. Enzyme-washed before it ships. For the full wash and care guide, see how to wash a heavyweight cotton hoodie.
We built it at 400gsm because 300gsm wasn’t the answer to the question we were asking. We wanted a hoodie that held its shape, replaced a jacket, and lasted. That’s a 400gsm decision. We made 200 units. We don’t restock.
"Fabric weight is a primary determinant of thermal performance and structural integrity in knitted fleece garments — higher GSM correlates directly with improved insulation and resistance to deformation under repeated wear." — Textile Institute
FAQ
What is the difference between 300gsm and 400gsm hoodies?
300gsm is a mid-weight fleece — lighter, more breathable, better for layering. 400gsm is a heavyweight fleece — denser, warmer, more structured, and significantly more durable. The 400gsm holds a silhouette; the 300gsm drapes loosely.
Is 400gsm too heavy for a hoodie?
No. 400gsm is the correct weight for a hoodie intended as an outer layer in UK autumn and winter conditions. It is heavier than most high-street options but not extreme — it is the standard weight used by premium heavyweight basics brands.
What GSM is a heavyweight hoodie?
350gsm and above is generally considered heavyweight. 400gsm is the premium standard. Below 300gsm is mid-weight; below 240gsm is lightweight.
Does a higher GSM hoodie last longer?
Yes. A denser fabric has more yarn to absorb wear and washing stress. At 400gsm with ring-spun cotton, surface pilling is significantly reduced compared to 280–300gsm alternatives. The garment holds its appearance and structure through far more wash cycles.
Is 400gsm hoodie worth it?
Yes, if the construction is genuine. A 400gsm ring-spun loop-back fleece hoodie will outlast multiple 300gsm alternatives and perform as an outer layer without a jacket. The cost-per-wear calculation consistently favours the heavier garment.
|
|
echelonn. aegis. 400gsm loop-back fleece · 100% ring-spun cotton · dropped shoulder · enzyme-washed · HQ 001 add to formation → |