Ask three suppliers for “carbon fiber fabric” and you will get three different materials at three different prices. The number that explains most of the difference is the fabric’s areal weight — quoted in grams per square metre (gsm). It is the first specification to fix when you design a laminate, because ply thickness, resin consumption and total part cost all follow from it.
What gsm actually measures
Areal weight is the mass of dry fiber per unit area of fabric. A 200 gsm fabric weighs 200 grams per square metre before any resin is added. It says nothing about the fiber type or the weave — a 200 gsm plain weave and a 200 gsm twill can behave very differently — but it is the primary driver of how thick each ply will be in the finished laminate.
Why weight matters more than most buyers expect
- Ply thickness. Heavier fabric builds thickness faster, so a laminate needs fewer plies. Fewer plies means less lay-up labour — often the largest cost in a hand lay-up part.
- Drape and conformity. Heavier fabric is stiffer and drapes poorly. On complex geometry, a heavy fabric can simply refuse to conform, forcing you to switch to a lighter grade.
- Resin consumption. Thicker fabrics need more resin to wet out and fill, which matters both for cost and for achieving the target fiber volume fraction.
- Surface finish. Lighter fabrics give a finer, more even weave pattern under clear coat; heavier fabrics read as a coarser texture.
- Cost per part. The cheapest fabric by the square metre is rarely the cheapest by the finished part — fewer plies can offset a higher unit price.
Common weights and where they belong
| Areal weight | Character | Typical use |
|---|---|---|
| ~100–200 gsm | Light, fine weave, excellent drape | Cosmetic surfaces, complex geometry, thin laminates, small parts |
| ~200–300 gsm | The general-purpose middle ground | Structural laminates, panels, most hand lay-up work |
| ~300–400 gsm | Heavier, stiffer, faster build | Flat structural panels, fewer plies required, industrial parts |
| ~400–600 gsm | Heavy, poor drape, industrial | Thick laminates, large flat parts, cost-driven industrial builds |
These bands are indicative rather than fixed rules. The right choice depends on your geometry and process more than on a catalogue number.
Estimating laminate thickness
A useful first approximation: a cured carbon fiber laminate ply is roughly 0.1 mm thick for every 200 gsm of fabric weight, at a typical fiber volume fraction. So:
- 200 gsm fabric → approximately 0.1 mm per ply
- 300 gsm fabric → approximately 0.15 mm per ply
- 400 gsm fabric → approximately 0.2 mm per ply
A 3 mm laminate therefore needs roughly 30 plies of 200 gsm fabric, or about 15 plies of 400 gsm. That difference in ply count is where the labour cost lives — and it is why industrial parts move to heavier fabrics while cosmetic parts stay light.
Treat this as a starting estimate for planning, not a design value. Resin content, fiber volume fraction and consolidation pressure all shift the actual result, so confirm thickness on a trial panel before committing tooling.
Weave and weight interact
Weight and weave are specified together, and the combination changes behavior in ways that matter:
- Light + plain weave — the most stable light fabric; good for flat cosmetic panels
- Light + twill — the best drape available; the standard choice for complex or curved parts
- Heavy + plain — stiff and hard to form; use on flat surfaces only
- Heavy + twill — balances build rate with some formability; common in structural work
Tow size interacts too: the same weight can be achieved with a 3K or a 12K tow, and the 12K version will be stiffer and coarser while the 3K version drapes better and looks finer. Our classification guide covers tow grades in detail.
How to choose, in practice
- Start from the process, not the fabric. Hand lay-up on complex geometry pushes you to light fabric. Press or automated processes tolerate heavier material.
- Work out the ply count your thickness implies. If the answer is 40 plies, the labour cost is the problem — go heavier.
- Check the drape limit. If the fabric will not conform to your geometry without wrinkles, no weight saving is worth it.
- Confirm finish requirements. If the surface will be visible under clear coat, the weave pattern is part of the specification.
- Confirm with a trial. Weight, resin content and pressing pressure interact. One test panel settles more questions than any calculator.
Specifying your fabric
We manufacture carbon fiber fabrics across the weight range discussed here — approximately 50 to 600 g/m² — in plain, twill and satin weaves, in widths up to 1270 mm. If you tell us the part, the process and the target thickness, we will confirm which weight and weave combination fits — including when a lighter, cheaper grade will do the job.
See carbon fiber fabrics for the full range, or send your specification through our contact page.
Related Reading
- Carbon Fiber Fabric Selection Guide — tow size, weave, weight and width
- Carbon Fiber Types & Classification — precursor, tow size and sizing
- Carbon vs Glass vs Aramid — choosing the right reinforcement