Grayscale Jacket

Grey jackets, measured — shades, weights and matches, not opinions

Materials guide

Jacket Fabric Weights Explained

Shell weight, mid-layer weight and fill power together decide how warm a jacket is — colour tells you nothing about any of them.

Fabric weight ranges by category in grams per square metre Range bars for nylon windbreaker shell, denim or canvas shell, fleece mid-layer and fully insulated jacket, plotted on a 0 to 900 grams per square metre axis. 0 900 g/m² Nylon shell 30–70 Denim/canvas 340–475 Fleece mid 200–350 Insulated 500–900
Fig. 1 — Shell, mid-layer and fully insulated weight ranges in g/m², drawn from Table 1.
Down fill power scale from entry level to premium A horizontal scale from 550 to 900 cubic inches per ounce showing the entry level and premium fill power bands for down insulation. 500 900 in³/oz 550 entry 700–900 premium
Fig. 2 — Fill power scale in cubic inches per ounce: 550 marks entry level down, 700–900 marks premium down.

Reading a Shell Weight

A plain-weave nylon windbreaker shell weighs 30 to 70 g/m² (about 0.9 to 2.1 oz/yd²) and adds almost no warmth on its own — it blocks wind and light rain. Denim and canvas jacket shells are far heavier at 10 to 14 oz/yd², which works out to roughly 340 to 475 g/m², and their weight comes from structure rather than insulation.

A fleece mid-layer, worn under a shell rather than as the shell itself, runs 200 to 350 g/m² (about 5.9 to 10.3 oz/yd²). A fully insulated jacket that combines shell and fill in one garment lands at 500 to 900 g/m² (about 14.7 to 26.5 oz/yd²) — roughly double a fleece mid-layer on its own, because it is doing the job of two layers at once.

Table 1 — Fabric and fill weights by category
Shell, mid-layer, insulated jacket and fill weights converted between g/m2 and oz/yd2 using 1 oz/yd2 = 33.9 g/m2.
Category g/m² oz/yd² Typical role
Nylon windbreaker shell 30–70 0.9–2.1 Wind and light rain layer, no insulation
Denim or canvas shell 340–475 10–14 Heavy structured shell, minimal built-in warmth
Fleece mid-layer 200–350 5.9–10.3 Worn under a shell, not weatherproof alone
Fully insulated jacket (shell + fill) 500–900 14.7–26.5 Combined cold-weather weight
Down fill, 550 fill power n/a – graded by fill power 150–300 g typical per jacket Entry-level warmth per gram of down
Down fill, 700–900 fill power n/a – graded by fill power 150–300 g typical per jacket Premium warmth per gram of down
Synthetic fill 60–200 1.8–5.9 Budget or wet-weather insulation
33.9 grams per square metre in one ounce per square yard, the constant used to convert every weight in Table 1

Fill Power vs Fill Weight

Down is graded by fill power, measured in cubic inches per ounce: 550 is entry level, and 700 to 900 is premium. A typical adult jacket holds 150 to 300 grams of down regardless of fill power grade, so two jackets with the same fill weight can perform very differently if one uses 550 fill power down and the other uses 800. Synthetic fill is quoted by weight per area instead, typically 60 to 200 g/m², because it does not loft the way down does.

Procedure: Estimate Warmth From a Listing

  1. 2 min

    Find the shell weight

    Look for a g/m² or oz/yd² figure in the spec sheet or product description.

    Typical failure: the listing only says "lightweight" or "midweight" with no number attached.
  2. 5 min

    Identify the layer structure

    Check whether the jacket is a single insulated shell or a shell meant to be worn over a separate mid-layer.

    Typical failure: the liner is described only as "quilted," with no weight given, so it is unclear whether it is a 60 g/m² or 200 g/m² synthetic fill.
  3. 2 min

    Check the fill power, if down-filled

    Accept 700 or higher for a jacket meant for cold-climate, three-season use.

    Typical failure: fill power is not listed at all, common on budget-line down jackets.
  4. 2 min

    Compare the fill weight to the typical range

    Check the fill weight against the 150 to 300 gram range typical for an adult jacket.

    Typical failure: only a size-range fill weight is given for the whole product line, not your specific size.
  5. 5 min

    Cross-check against Table 1

    Place the shell and fill numbers next to the category ranges above to see where the jacket actually sits.

    Typical failure: the shell fabric blend is given as "poly-cotton" with no percentage split, making the weight figure harder to interpret.

Questions About Weight and Warmth

Is a heavier jacket always warmer?

Not necessarily. A heavy denim shell at 475 g/m² has almost no insulation built in, while a lighter-feeling jacket with 800 fill power down can trap more warm air per gram. Weight alone does not separate structure from insulation.

What's fill power and why does it matter more than fill weight?

Fill power measures how much a given weight of down lofts, in cubic inches per ounce. Higher fill power traps more warm air per gram of down, so a jacket with less down at 800 fill power can be as warm as one with more down at 550 fill power.

Can I add a liner to a 30 g/m² windbreaker shell?

A windbreaker shell at 30 to 70 g/m² is built for wind and light rain, not insulation. Adding a fleece mid-layer at 200 to 350 g/m² underneath is the standard way to add warmth without buying a fully insulated jacket.