Fabric consumption per garment, and how to calculate it
How much cloth one garment uses, waste included, how a woven cloth's weight follows from its construction, and why the factory's figure will not match yours.
Fabric is usually the largest line in the cost of a garment, and the number behind that line is consumption: how much cloth one garment uses, waste included. Brands are asked for it, or quoted against it, long before anyone explains how it is worked out. This page separates the two numbers that get confused, consumption and fabric weight, shows how a woven cloth’s weight follows from its construction with the arithmetic written out, and sets out what moves the consumption of the same garment from one order to the next. It ends with why the factory’s figure will not match yours, and what to ask.
What you are actually being asked for
When a factory quotes a fabric cost, it is working from one figure: how much cloth one garment uses, including the waste between the pieces. That figure is decided by three things, the pattern, the size ratio, and how efficiently the pieces are laid out on the cloth. It is usually the largest single line in the cost, often half of it or more, which makes it the first place to look when a price seems high.
So the useful conversation is not about the fabric price alone. It is about the fabric price multiplied by this figure, and the figure is the half that a brand can often change.
The two numbers people confuse
Consumption
The length of cloth one garment uses, in metres or yards, cutting waste included. It belongs to the garment: the same cloth gives a different consumption for a shirt, a dress and a pair of trousers.
Fabric weight, or GSM
Grams per square metre, the standard measure of how heavy a cloth is. It belongs to the cloth: the same garment made in a heavier cloth uses the same metres, and those metres weigh more.
The two meet in one line of arithmetic. One running metre of cloth weighs its GSM multiplied by its width in metres, so the cloth in one garment weighs the metres it uses multiplied by that. Keep the two apart in a conversation, and a quote that confuses them becomes easy to spot.
Calculating GSM from the construction
A woven construction is a weight in disguise. Two counts and two densities are enough to give the grams per square metre before a metre is woven. With the counts in English cotton count, Ne, and the densities in threads per inch:
GSM = 23.25 × [ ends per inch × (1 + warp allowance) ÷ warp count + picks per inch × (1 + weft allowance) ÷ weft count ]
The allowances are for crimp: a thread waves over and under the threads crossing it, so it uses more length than the cloth is long. Take a 20s by 20s twill, 108 ends and 56 picks per inch, 63 inches wide, with 10 per cent allowed on the warp and 5 per cent on the weft:
23.25 × [ 108 × 1.10 ÷ 20 + 56 × 1.05 ÷ 20 ] = 23.25 × [ 5.94 + 2.94 ] = about 206 grams per square metre
At 63 inches, which is 1.60 metres, one running metre of that cloth weighs about 330 grams. Every metre the marker uses for one garment in this cloth is that much fabric.
The allowances are planning figures, not a specification, and so is the result. It tells you what to expect and what to question. Only a sealed sample and a test report tell you what you are buying. The fabric weight calculator does the arithmetic for your own construction, and the worked examples in the raw material guide take a poplin, this twill and a denim through the same steps.
What moves consumption on the same garment
Four things, and a brand decides at least two of them before the factory ever sees the tech pack.
The marker, and the width
The marker is the layout of every pattern piece for the whole size ratio on the cloth, and marker efficiency is the share of the laid cloth that ends up as garment pieces rather than offcut. A few points of it are worth more than most of the negotiating anyone does on the making charge. The width that matters is the cuttable width, inside the selvedge, not the width on the label: a cloth a few centimetres narrower than promised can cost a whole size in the marker.
The size run
A marker is made for a size ratio, so a run weighted to the larger sizes uses more cloth per garment than the same quantity weighted to the smaller ones. A consumption quoted for one sample size is not the consumption of the order.
Print direction, nap and stripe matching
A one way print, a napped cloth such as corduroy or velvet, and a stripe or check that must match across the seams all stop the pieces being turned or nested wherever they fit best, so the marker leaves more offcut. Say so in the tech pack, or the first consumption figure will be too low.
Wastage, and who carries it
Beyond the offcut inside the marker, cloth is lost at the ends of each roll and each lay, to flaws cut out after inspection, and to shrinkage if the cloth is relaxed or washed before cutting. And a garment should never be cut across two shade lots, so a lot too short for a full lay leaves a remainder. Ask whether the consumption you are given already includes these, and who pays for the extra cloth if the order needs more than was bought.
Knits are counted differently from wovens
A knit’s weight is measured on the finished cloth, and the yarn it needs is worked backwards from that weight, with an allowance for knitting waste, dyeing loss and inspection cuts. So a knitted cloth’s GSM is a number to specify, with a tolerance, rather than one to calculate.
Two knit questions change the marker. Is the cloth tubular or open width? Tubular has no side seam, which changes the pattern itself. And what are its shrinkage and its spirality, the twist that makes a side seam walk round the body after washing? Both have to be settled before a consumption figure for a knit means anything.
Why the factory’s figure differs from yours
Your figure and the factory’s will not match, and neither needs to be wrong. The factory works on its own marker for your whole size ratio, where you may have worked on one size. It works on the cuttable width, where you may have used the full width. It adds its own wastage allowance, where you may have added none. And greige cloth and finished cloth are different widths and different weights for the same construction, so a figure worked on one does not hold for the other.
The same is true one step back, at the mill. Mills carry their own crimp allowances by loom and by construction, so a weight you calculate is a planning figure and the mill’s measured one is the number on the contract.
So treat your figure as the one to question the quote with, not the one to insist on. Ask for the width, the size ratio and the allowances behind theirs, and the two can be reconciled line by line. The same reasoning sits behind the minimum order, on minimum order quantity, explained.
Common questions
How much fabric does a garment take?
It depends on the pattern, the size ratio, the cuttable width of the cloth and how efficiently the pieces are laid out, so there is no honest single figure for a shirt or a tee. The factory's pattern maker gets it from the marker for your pattern, and that is the figure to ask for.
How do you work out a fabric's weight from its construction?
From the two counts and the two densities. Grams per square metre is about 23.25 times the sum of ends per inch divided by the warp count and picks per inch divided by the weft count, each with an allowance for crimp. The calculator does it for you, and a sealed sample confirms it.
Does the consumption figure include wastage?
It should include the cutting waste between the pieces, but end of roll losses, flaws, shrinkage and shade lot remainders are sometimes carried separately. Ask in writing what is inside the figure, so two factories' numbers compare.
Why is the factory's consumption figure different from mine?
Because it is worked on the factory's own marker for the whole size ratio, on the cuttable width rather than the full width, with its own wastage allowance, and because greige and finished cloth are different widths and weights. Ask for the width and the allowances behind it, and the two can be reconciled.