Topic: Metals and industrial parts · Published · Updated · Version 1
Sheet metal: what to specify in a request
A sheet or plate request should name the alloy or grade and the standard that defines that name, the thickness in millimetres, the sheet size, and the quantity. A title such as “sheet metal”, or a gauge number on its own, is not a complete description. This page is general information, not a design calculation. It does not publish a gauge-to-millimetre chart, and it does not say that any listing meets a standard or is cut to a stated size.
Write a description a quotation can be checked against
Sheet and plate are quoted against a description. The request should make that description checkable, item by item:
- Alloy or grade, including the standard that defines the name you used. A nickname without a standards body is incomplete. The companion guide on steel grades and standards explains why the full designation matters for steel; the same habit applies when the sheet is another metal: name the standard, not only a familiar shorthand.
- Thickness, in millimetres, and the sheet or blank size (width and length, or the coil width, as applicable). State the unit.
- Temper, hardness, surface condition or finish when your job depends on them. If you do not say, a later quotation cannot be checked against those requirements.
- Quantity, as a sheet count or as a mass, and say which of those you mean.
- Destination, and whether the quotation should include cutting to size. Cutting is not assumed.
NIST Special Publication 811, Guide for the Use of the International System of Units (SI), is the writing reference this guide uses for expressing a thickness or a length with its unit. NIST presents SP 811 as its guide to SI practice (2008 edition). It is not a sheet-metal product standard, and it is not a gauge chart.
Thickness should be a measured value, not only a gauge number
This page does not publish a conversion from gauge numbers to millimetres, and it does not treat a gauge number as a complete thickness. A request that says only “16 gauge”, or only “16 ga”, does not, by itself, state a thickness in millimetres. No single official worldwide gauge scale was verified for this article; any specific gauge-to-millimetre value is therefore UNKNOWN here and is not tabulated.
Write the thickness as a number and a unit, preferably in millimetres, following the SI writing practice pointed to by NIST SP 811. If your drawing also shows a gauge number, you may copy it in addition to the millimetre thickness, and say which gauge system the drawing names, if it names one. The millimetre value is still the thickness this guide asks you to state.
The cut-off at which a product is called “sheet” rather than “plate” is also UNKNOWN here, because that boundary is not a single worldwide figure in the sources opened for this article. Name the thickness and the product form, rather than relying on the word “sheet” or “plate” alone.
A material family is not a part specification
If the metal is steel, worldsteel’s About steel page describes strength, ductility, conductivity and magnetism among the properties that explain why steel is widely used. Its What is steel? page states that there are more than 3,500 different grades of steel, with many different physical, chemical and environmental properties. Those statements describe a material family. They do not specify a sheet for a job, and they are not a substitute for the grade, the standard, the thickness and the size in your request.
This guide does not recommend an alloy, a temper, a surface or a forming process. Whether a named product is suitable for a given forming, welding, pressure, food-contact or structural use is UNKNOWN here and is not implied by a catalogue title.
What this site will not fill in for you
Global Market keeps supplier and brand identities off the page. A listing does not become a certified sheet, a stated thickness tolerance, or a cutting service because it sits in the catalogue. On 10 November 2026 the homepage described the visible listings as a synthetic storefront demonstration, not real offers. This article does not restate listing figures and does not promise stock, certificates or a dispatch date.
If no current listing matches the sheet you need, a sourcing request can still carry the points above. The request is not an order and it does not take payment. Do not expect the request form, or this page, to choose a grade, convert a gauge number, or decide a tolerance class.
Frequently asked questions
Is a gauge number enough if everyone in my trade uses it? Not on this page. Give the thickness in millimetres, with the unit. You may also copy a gauge number from the drawing, but this guide does not convert it and does not treat it as a complete thickness.
What is the thickness at which sheet becomes plate? UNKNOWN here. Name the thickness and the form. Do not rely on the word alone.
Do I have to state temper or surface? State them when the job depends on them. If you omit them, they are not requirements a later quotation can be checked against.
Does a listing that says “sheet metal” meet my drawing? No listing on this site is certified by this page. Match the request to the drawing, and confirm the offer in a written quotation.
Sources
Read 10 November 2026, Asia/Singapore (UTC+8).
- Special Publication 811: Guide for the Use of the International System of Units (SI) — National Institute of Standards and Technology
- About steel — World Steel Association
- What is steel? — World Steel Association
Related
Steel: name the standard and the grade · How to send a sourcing request · Sourcing guides