A weight number is useful only when its unit and measurement basis are clear. Before comparing Melton specifications or quotations, establish whether the figure describes mass per square metre, mass per linear metre or another basis. Then record the width that corresponds to that figure. This prevents a conversion from creating a precise-looking answer for the wrong piece of material.
1. Preserve the supplier's original weight statement
Copy the value and unit exactly as supplied, together with the article, colour, revision and date. GSM means grams per square metre. A value in g/linear m describes the mass of a length across its stated width. Those quantities are related only when the width and area basis correspond. A label such as '600 g' without a denominator is incomplete; do not choose its meaning from the size of the number.
Ask whether the figure is nominal, a measurement of this sample, or an agreed specification range. Keep those statuses distinct. A buyer target is not a supplier result, and a supplier's nominal figure is not automatically the accepted tolerance. If a photograph shows a label, preserve it as evidence and request a legible current specification before treating it as a fixed purchasing condition.
2. Separate total width from usable width
Total width and usable width answer different questions. The usable width is relevant to the pattern layout under the project's agreed definition. The mass of a full-width strip must be associated with the corresponding measured width and material basis. Do not silently substitute usable width for total width when converting a full-strip linear mass. Ask how selvedges and unusable edge areas are treated in the supplied figures.
Record both widths, their units and their source where known. If only usable width is supplied, mark total width as unknown rather than calculating it. Conversely, a quoted total width does not prove the area available to the pattern maker. Where construction or edge variation makes simple conversion inappropriate, preserve the measured quantities and ask the supplier or laboratory for the matching method and basis.
3. Convert only matching quantities
For a consistently described area, g/linear m = GSM × width in metres; GSM = g/linear m ÷ width in metres. An arithmetic example is 500 GSM × 1.5 m = 750 g/linear m. Reversing the same inputs gives 750 ÷ 1.5 = 500 GSM. These are calculation examples, not specifications or tolerances for a supplied Melton article.
Enter width in a stated unit and convert it before using the formula. One international yard is exactly 0.9144 m, and one inch is exactly 0.0254 m. For oz/yd², convert the mass and square-yard area together; the site's calculator shows the entered values and arithmetic. A positive numerical result does not repair an unknown width basis. Keep the original input beside the converted figure so a colleague can audit the calculation.
4. Keep measurement conditions and evidence attached
When weight is important to acceptance, agree how the measurement will be made, which samples it represents and what conditions apply. Ask for a report or applicable specification with sample identity, method, result, units and date. ISO 3801 concerns mass per unit length and mass per unit area of woven fabrics; citing its catalogue scope does not establish that a particular Fred sample was tested to it.
Record the relevant evidence rather than adding a standards logo to a product card. If two figures were produced on different states or bases, clarify that difference before ranking the references. Do not convert a dry-looking or damp-feeling handling observation into a corrected GSM. Where a contractual method or tolerance is needed, have the buyer, supplier and testing party agree it explicitly.
5. Define buyer ranges without inventing supplier acceptance
Write the target as a buyer requirement, including the unit and whether it is fixed or open for recommendation. If a range is essential, explain the garment reason and which decisions depend on it. A requested range is not proof that the current article falls within it. Leave a separate field for Fred's confirmed information and another for any agreed tolerance and measurement procedure.
GSM does not uniquely specify thickness, bending behaviour, warmth, durability or finished garment weight. Choose any further evidence from the actual question: a separate thickness measurement, a broad hanging comparison, a local collar trial or an agreed performance test. Avoid replacing several garment decisions with one weight threshold. A sample outside a preference can still be discussed; a sample lacking proof against a fixed requirement remains unconfirmed.
6. Carry the same basis into the brief and quotation
Use one current specification revision when asking several questions or comparing replies. State weight value and unit, total width, usable width, article/colour identity and evidence status. If a price is per metre, preserve that unit separately from GSM. Converting mass units does not convert a quotation or establish garment consumption.
Before estimating fabric area mass, distinguish a full-area estimate from a usable-area estimate. GSM × width in metres × length in metres ÷ 1000 gives kilograms for the described area under matching assumptions. It excludes packaging and is not a shipping weight. Ask the pattern maker to estimate length from the real layout, and ask Fred to confirm the commercial quantity basis. Export the unresolved width and measurement questions alongside the calculation.
| Field | Buyer entry | Supplier evidence | Decision check |
|---|---|---|---|
| Weight | Value + GSM/g per linear m/oz per square yard | Sample/specification revision and measurement basis | Are we comparing the same quantity? |
| Total width | Value + unit, or unknown | Definition and measured material | Does this match the linear mass? |
| Usable width | Value + unit, or unknown | Agreed usable-area definition | Can the pattern layout use this area? |
| Tolerance | Requested, not yet agreed | Method and accepted range if agreed | Who confirmed this and for which revision? |
Questions before your next sample
Can 600 g per metre be called 600 GSM?
No. You need the matching width and measurement basis to convert linear mass to mass per area.
Can I use usable width to estimate a whole roll's mass?
Only if the intended estimate explicitly describes that usable area. It must not be labelled the mass of the entire roll without the corresponding full-area basis.
Does equal GSM mean equal thickness?
No. Ask for thickness measured separately with its method and conditions, and trial the actual garment layers.
Evidence and measurement references
These sources support measurement or care context; they are not product-specific Fred Textile test reports.
Troubleshoot two figures that appear to disagree
Consider a card with a clear GSM value and a reply containing a number followed only by 'g/m'. Do not select a width and force the two figures to match. Ask what length or area the second number describes, which width belongs to that measurement and whether both records concern the same article revision. Preserve the original wording and attach the clarification beside it. If the supplier corrects a unit or width, recalculate from the corrected source rather than editing only the displayed answer.
Then identify the decision that actually needs the converted value. A mass comparison may require a matching full-width basis, while a pattern layout needs an applicable usable width. Neither calculation establishes how many metres the pattern consumes. If a quotation uses another commercial unit, request that basis explicitly and keep it separate from the technical conversion. Where a fixed acceptance range matters, leave the candidate pending until the applicable evidence and agreed measurement basis are available. An unexplained difference is a question to resolve, not proof that the fabric is defective or that one supplier's material is superior. Keep the former value in the revision history so everyone can see why the estimate changed.
Two numbers disagree: fix the comparison basis before selecting a value
Keep the original supplier statement and the buyer's calculation in separate fields. Identify whether each number concerns area mass, linear mass or an entered area estimate, and attach the width used in any conversion. A linear-weight value based on total material width cannot be fairly checked with a narrower usable-width figure without explaining the changed area. Ask the supplier which width and material state correspond to the stated weight; do not choose whichever calculation falls inside the target range.
If the basis is already the same and the discrepancy remains, preserve the result as unresolved. Ask what measurement or current specification should be used for this identified cutting, with the method and relevant conditions recorded where numerical acceptance matters. Do not average conflicting statements into a new specification or invent an acceptable tolerance. The person responsible for the project must agree the requirement and review the evidence. Until then, carry the original values, the open question and the next action into the comparison rather than declaring the sample within specification.