Choosing Outdoor Fabric for Bags, Tents and Covers
Outdoor fabrics are sold on a handful of numbers: a denier such as 70D or 600D, a weight in ounces or grams, a coating, and sometimes a waterproof rating. Those numbers are enough to choose sensibly between a tent fly, a rucksack body and a patio cover, once you know what each one measures. This guide explains them, converts the common deniers and weights with the site's yarn count converter and Fabric Weight Converter, and works through the yardage and weight of a simple cover with the Fabric Yardage Calculator and Fabric Weight from Dimensions tool.
Denier: the yarn, not the fabric
The "D" number on an outdoor fabric is the linear density of the yarn it is woven from, in denier: the mass in grams of 9,000 metres of that yarn. It is not the fabric's weight, though heavier yarns generally make heavier fabrics. In the converter:
| Yarn | Tex | Dtex | Typical outdoor use |
|---|---|---|---|
| 20D | 2.22 | 22.22 | Ultralight shells, tent flies, down-proof liners |
| 70D | 7.78 | 77.78 | General-purpose shells, linings, lighter tent floors |
| 210D | 23.33 | 233.33 | Pack bodies, tent floors, stuff sacks |
| 420D | 46.67 | 466.67 | Hard-wearing pack bodies and bases |
| 600D | 66.67 | 666.67 | Bags, luggage, covers |
| 1000D | 111.11 | 1111.11 | Heavy-duty packs, luggage, tool bags |
A higher denier usually means better abrasion and puncture resistance and more weight. The fibre matters as well: nylon is generally tougher than polyester at the same denier, while polyester stretches less when wet and holds up better in sunlight. Many fabrics give a denier for warp and weft separately, and some, such as ripstops, include a heavier reinforcing yarn at intervals.
Fabric weight: ounces and grams
Outdoor fabric weights are often given in ounces per square yard, especially by American suppliers, and in grams per square metre elsewhere. The converter gives the exact figure either way. A "1.1 oz" ultralight silicone-coated nylon is 37.3 GSM; a 300 GSM solution-dyed acrylic awning canvas is 8.85 oz/yd².
Check whether the weight is for the base fabric or the finished, coated fabric. Coatings add a lot: a light silicone coat adds a few grams per square metre, while a heavy PVC coat can be the larger part of the total. The guide to coated fabrics and tarpaulins works through that split.
Weave and construction
- Ripstop: a fine fabric with heavier yarns woven in at intervals to form a grid. A tear tends to stop at the next heavy yarn. Common for tents, shells and lightweight packs.
- Oxford and plain weaves: simple, strong, widely used for packs and bags. Oxford fabrics often use doubled yarns.
- Canvas and duck: heavy plain weaves of cotton, polyester, acrylic or blends, used for awnings, covers, tents and bags.
- Textured nylon: air-jet-textured yarns give a cotton-like surface and good abrasion resistance at a given weight.
Weave density matters as much as yarn size for wind resistance and for how well a coating sits on the fabric.
Coatings and finishes
- PU (polyurethane): common on pack fabrics and tent floors. Can be seam-taped. Some PU coatings break down slowly with heat, humidity and age.
- Silicone: on lightweight tents and tarps. Very water-repellent and adds tear strength, but is hard to tape or glue, so seams are usually sealed with a silicone sealant.
- PVC: heavy covers and tarpaulins. Very durable and weldable, but heavy and stiff.
- DWR (durable water repellent): a surface finish that makes water bead and roll off. It wears off over time and can be renewed. Some older DWR chemistries are now restricted in a number of countries.
Waterproof claims are usually expressed as a hydrostatic head in millimetres, the height of water column a fabric withstands before leaking. The guide to waterproof fabric ratings explains how to read those figures and why test methods differ.
Sunlight
Ultraviolet light breaks down most fibres over time. For things that live outside, such as awnings, boat covers, sun shades and garden furniture, fibre choice matters:
- solution-dyed acrylic and solution-dyed polyester, where colour is added before the fibre is formed, resist fading well and are widely used for awnings and cushions;
- nylon loses strength faster in strong sunlight than polyester;
- coatings and the thread used to sew them also degrade. Ordinary polyester or cotton thread can rot in the sun long before the fabric does. UV-resistant thread, such as bonded polyester rated for outdoor use or PTFE thread, lasts much longer.
Worked example: a simple cover
Suppose a cover for garden furniture or a small boat needs about 6 m² of fabric once hems and overlaps are included, and the fabric is 150 cm wide with about 145 cm usable after trimming the selvedges.
- Length to buy. With 6 m², 145 cm usable width and a 10% waste allowance, the yardage calculator gives 4.14 m before waste and 4.55 m to buy, or 4.98 yards.
- Weight of the fabric. In a 300 GSM awning canvas, 4.55 m at 150 cm is 6.82 m², weighing 2.05 kg, or 450 g per running metre.
The weight matters if the cover will be lifted on and off often, or tied over a frame. A wet cover weighs more, and a cover that catches wind puts real load on its tie-downs.
The yardage calculator works from total area and does not plan a cutting layout. If the cover has panels wider than the fabric, they need seams, and the number of full-width panels can push the real requirement above the area-based estimate. Sketch the panels on the fabric width before ordering.
Choosing for the job
- Ultralight tent or tarp: 20D to 30D silicone-coated nylon or polyester ripstop, roughly 35 to 50 GSM. Light and packable, but needs care with abrasion and sharp ground.
- General tent fly or shell: 40D to 70D, coated or with a membrane for clothing.
- Pack body: 210D to 500D nylon, often PU-coated; heavier at the base.
- Luggage and tool bags: 600D to 1000D polyester or nylon.
- Awnings, furniture and boat covers: solution-dyed acrylic or polyester canvas, or PVC-coated polyester for full waterproofing.
These are broad guides, not rules. A thoughtful design in a lighter fabric often outlasts a careless one in a heavier fabric.
Repairing outdoor fabric
Outdoor fabrics are worth repairing, and the fabric type decides how. Small holes and tears in coated nylon and polyester can be patched with self-adhesive repair tape made for the purpose, applied to clean, dry fabric with rounded corners so the edges do not lift. Silicone-coated fabrics need repair products designed for silicone, because ordinary tapes and glues do not stick to it. PVC-coated covers and tarps can be patched with PVC repair kits or welded patches. Canvas can be darned or patched with a sewn patch, then re-proofed. For seams that leak, reseal them with the sealer suited to the coating. Keep a note of each fabric's type and coating when you buy or make gear: it saves guessing at the repair stage, and the denier and weight figures help you choose a patch fabric of similar strength.
Safety around tents and covers
Most outdoor fabrics are flammable, and synthetic fabrics can melt as well as burn. Keep stoves, heaters, candles and barbecues well away from tents, awnings and covers. Never use a stove, heater or barbecue inside a tent or enclosed awning: as well as the fire risk, burning fuel produces carbon monoxide, which can kill without warning in an enclosed space. Some tents and event structures must meet flame-resistance requirements; if you are making or supplying one for public use, check your local rules and use certified fabric.
What the tools cover
The converters give exact denier, tex and dtex for yarns, and GSM and ounces for fabrics. The yardage and dimensions tools give you a length to buy and the weight of what you buy. None of them can tell you how a fabric resists abrasion, tearing, sunlight or water; those come from the maker's test data. Use the numbers to compare like with like, and ask for test results to a named standard when performance matters.