On your first day selling steel, someone probably tossed around the words coil, sheet, and plate like you should already know the difference. Nobody explained it clearly. Here is the explanation you should have received.
Coil
A coil is a continuous strip of flat-rolled steel wound into a roll. Think of a roll of aluminum foil, except it weighs 20,000 to 50,000 pounds and the strip can be 1,000 to 5,000 feet long.
Coils are how mills produce and ship most flat-rolled steel. It is more efficient to roll a continuous strip and coil it than to cut individual pieces at the mill. The service center receives the coil and either sells it as-is (to customers who have their own processing equipment) or processes it into sheets, strips, or blanks.
Coils are defined by gauge (thickness), width, weight, grade, and coating. A "20,000-pound coil of 16-gauge CRC at 48 inches" means a cold-rolled carbon steel coil that is 0.0598 inches thick, 48 inches wide, and weighs 20,000 pounds. The length is calculated from the weight, width, and gauge.
Common processing: slitting (cutting the coil into narrower strips), cut-to-length (unrolling and shearing into flat sheets), and leveling (flattening any coil set or crossbow to produce flat sheets).
Sheet
A sheet is a flat piece of steel cut from a coil. Sheets are defined by gauge, width, and length. A "14-gauge HRC sheet at 48 x 120 inches" is a hot-rolled carbon steel sheet that is 0.0747 inches thick, 48 inches wide, and 120 inches long.
The distinction between sheet and plate is based on thickness, though the exact cutoff varies by convention. Generally, material 3/16 inch (0.1875") and thinner is called sheet. Material thicker than 3/16 inch is called plate. Some sources draw the line at 1/4 inch (0.250"). The important thing is that your service center uses a consistent definition and your customers understand which one you are using.
Sheets are sold by the piece or by weight. A customer ordering "20 sheets of 14-gauge HRC at 48 x 120" is ordering 20 individual flat pieces. The total weight is calculated from the dimensions and gauge.
Plate
Plate is thick flat steel, typically 3/16 inch and above, up to several inches thick. Plate is usually produced differently from sheet. Thin plate (3/16" to 1/2") may come from coil (coil plate). Heavy plate (1/2" and above) is typically produced as discrete plates on a plate mill, not from coil.
Plate is defined by thickness, width, length, and grade. A "1/2-inch A36 plate at 60 x 120 inches" is a carbon steel plate that is 0.500 inches thick, 60 inches wide, and 120 inches long. It weighs approximately 1,020 pounds (calculated from dimensions and density).
Plate is commonly used in structural applications (base plates, connection plates, gusset plates), machine bases, pressure vessel components, and wear applications. Plate customers are often fabricators who will cut, drill, and weld the plate into finished components.
Why It Matters for Sales
Knowing the product form matters because it affects every part of the transaction.
Pricing. Coil is typically the lowest-cost form because it requires no processing at the service center. Sheet is more expensive because it has been cut to length (processing charge added). Plate pricing varies by thickness and grade, with heavier plate often carrying higher per-pound costs.
Availability. Coil is available in standard widths from the mill. Sheets are available in whatever sizes the service center has cut or can cut. Plate is available in standard mill sizes or can be cut to custom dimensions (flame cut, plasma cut, or waterjet cut).
Customer needs. A stamping plant needs coil (they feed it into their presses). A metal building manufacturer needs sheets (pre-cut to specific panel sizes). A structural steel fabricator needs plate (cut and welded into connections and components). Understanding the product form tells you what the customer does with the material and how they need it delivered.
Lead time. Coil from inventory ships in 1 to 3 days. Sheet cut from coil adds 1 to 3 days for processing. Plate from inventory ships in 1 to 3 days. Custom-cut plate adds processing time based on the complexity of the cut and the shop's schedule.
This is the foundation. Everything else you learn about selling steel builds on understanding what the customer needs: coil, sheet, or plate, in what grade, at what dimensions, with what processing, delivered where and when. Get these basics right and the rest follows.