Metal roof panel widths and coverage are two different numbers, and ordering off the wrong one is the most common way a metal roof order comes up short. Overall width is the sheet measured edge to edge. Net coverage is what is left after the side lap is buried under the next panel. On a 7/8 inch corrugated panel from Western States Metal Roofing, those two numbers are 39 inches and 34.67 inches. Order 480 inches of eave off the 39 inch figure and you are one full panel short before you start.
By The Roofing Brief Team. Last reviewed: August 2026.
Overall width versus net coverage: the number that causes short orders
Overall width is the physical width of the sheet on the truck. Net coverage is the width of finished roof each panel contributes once it is lapped into the panel beside it. Panel counts must always be figured on net coverage. The gap between the two numbers is the side lap, and it is paid for on every single panel in the order, not once at the end of the run.
Exposed fastener profiles split into two camps by how they publish the number. R-panel, PBR and 7.2 profiles are almost always published as coverage, so 36 inches means 36 inches of roof. Corrugated and 5V are frequently sold by the sheet size, so the number on the price list is the overall width and the coverage is smaller.
Western States Metal Roofing states the penalty directly for its own product: 7/8 inch corrugated at 39 inches overall yields 34.67 inches of roof coverage, so a buyer needs approximately 12 percent additional material because of the panel side lap. On the same maker’s 1/2 inch corrugated, 26 inches overall yields 21.33 inches of coverage, which they put at approximately 23 percent additional material.
Metal roof panel widths and coverage by profile
Every figure below comes from the named manufacturer’s own published literature. Coverage is not a property of a profile family, it is a property of a specific manufacturer’s tooling, so the maker’s name belongs beside every number you put in a takeoff.
Exposed fastener panels
| Profile (manufacturer) | Overall sheet width | Net roof coverage | Rib height and spacing | Minimum slope | Support |
|---|---|---|---|---|---|
| R-Panel, 26 ga (McElroy Metal) | Published as coverage | 36 in | 1 1/4 in rib at 12 in o.c. | 1:12 with sealant, 3:12 without | Solid deck or open framing |
| PBR / R-Loc, 26 ga (Central States) | Published as coverage | 36 in | 1 1/4 in rib at 12 in o.c. | Per manufacturer | Purlin bearing leg at side lap |
| 7.2 Panel, 24 ga (MBCI) | Published as coverage | 36 in | 1 1/2 in rib at 7.2 in o.c. | 1/2:12 | Exposed fastener, open framing |
| Western Rib 7.2 (Western States) | Published as coverage | 36 in | 1.5 in rib at 7.2 in pitch | 1/12 | Open purlin or solid substrate |
| Mega-Rib 7.2, 26 ga (McElroy Metal) | Published as coverage | 36 in from the Adelanto plant, 28.8 in from all other McElroy locations | 1 1/2 in rib at 7.2 in o.c. | 1:12, tape sealant at all slopes | Solid deck or open framing |
| 7/8 in corrugated, PVDF finish (Western States) | 39 in | 34.67 in roof, 37 in wall | 7/8 in deep at 2.67 in pitch | 3/12 | Exposed fastener |
| 7/8 in corrugated, SMP finish (Western States) | 37 in | 32 in roof, 34.67 in wall | 7/8 in deep at 2.67 in pitch | 3/12 | Exposed fastener |
| 1/2 in corrugated (Western States) | 26 in | 21.33 in roof | 1/2 in deep | Per manufacturer | Exposed fastener |
| 5V Crimp (A.B. Martin) | 26 in | 24 in | 1 in by 1/2 in rib every 12 in | Per manufacturer | Solid deck |
| 5V, 26 ga (McElroy Metal) | Published as coverage | 24 in | 1/2 in rib at 12 in o.c. | 3:12 | Solid deck |
| 5V Crimp, 29 ga standard (MBCI) | Published as coverage | 24 in | 1/2 in rib at 12 in o.c. | 3:12 | Solid deck with waterproof underlayment |
| 5V Crimp (Gulf Coast Supply, FL34538.08-R3) | Published as coverage | 24 in nominal maximum | 7/16 in nominal rib | Per Florida Building Code | 15/32 in minimum plywood or 3/4 in plank |
Standing seam panels
| System (manufacturer) | Coverage widths offered | Seam height | Minimum slope | Support |
|---|---|---|---|---|
| 138T mechanically seamed (McElroy Metal) | 12 in, 16 in, 18 in | 1 3/8 in | 1:12 | Solid deck only |
| 238T mechanically seamed (McElroy Metal) | 16 in, 18 in, 24 in (24 in site formed only) | 2 3/8 in | 1/2:12 | Solid deck or open framing |
| LokSeam snap together (MBCI) | 12 in, 16 in, 18 in | 1 3/4 in | 3:12 | Open framing or solid substructure |
| Western Lock snap lock (Western States) | 18 in standard, 12 in, 14 in and 16 in alternates, custom 12 in to 20 in | 1.75 in | 3/12 | Solid substrate with underlayment |
The Western Lock data sheet publishes something most literature hides: a coil feed of 24 inches producing 18 inches of standard coverage. Six inches of every 24 inch strip of coil goes into the two seams. That is the real cost of a concealed fastener system in raw material, and it is why standing seam carries a higher material price per square than a 36 inch exposed fastener panel of the same gauge.
Why two panels with the same profile name give different coverage
Profile names are not standards. They are trade names, and the coverage attached to them varies by manufacturer, by plant, and even by paint system. Three verified examples from the literature above show how wide the spread gets on panels that all sound identical on a purchase order.
- Same profile, different plant. McElroy Metal publishes Mega-Rib 26 gauge coverage as 36 inches from its Adelanto facility and 28.8 inches from every other McElroy location. That is a 20 percent swing on the same product name.
- Same profile, different paint. Western States Metal Roofing runs 7/8 inch corrugated at 39 inches overall and 34.67 inches of roof coverage in PVDF, but 37 inches overall and 32 inches of coverage in SMP, because the two finishes come off different coil widths.
- Same profile, different application. That same 7/8 inch corrugated panel covers 34.67 inches on a roof and 37 inches on a wall. The panel did not change. The number of corrugations in the lap did.
5V is the other reliable trap. McElroy Metal, MBCI and Gulf Coast Supply all publish 24 inches of coverage, but 21 inch coverage 5V is also sold in the market, so the profile name alone does not fix the number. Ask for the coverage figure in writing before the order is released.
How to count panels for a roof plane
Panel count is the eave length of the plane divided by net coverage, rounded up. The side lap is already inside the net coverage figure, so it is never subtracted a second time. Work in inches, work one plane at a time, and never mix a coverage number from one manufacturer with a price from another.
- Measure the eave length of the plane in inches. A 40 foot plane is 480 inches. Include rake overhangs.
- Get net coverage in writing from the supplying manufacturer. Not the profile name, not the sheet width on the invoice.
- Divide and round up. Fractions of a panel do not exist. A 0.1 remainder still costs a full panel.
- Check that the last panel can actually be ripped. On R-panel and corrugated the rip lands in a flat pan or a corrugation and is fine. On standing seam a ripped panel loses one seam leg and needs a rake or wall detail, so plan the starting edge to avoid a sliver.
- Repeat per plane, then add length allowances. Panel length is a separate calculation covered in our guide to metal roofing panel lengths, including overhang, hem and thermal limits.
Applied to one 40 foot by 18 foot plane, the same roof takes very different panel counts depending on profile:
| Profile | Net coverage | 480 in divided by coverage | Panels to order | Coverage bought |
|---|---|---|---|---|
| R-panel or PBR (McElroy, Central States) | 36 in | 13.3 | 14 | 504 in |
| 7/8 in corrugated, PVDF (Western States) | 34.67 in | 13.8 | 14 | 485.4 in |
| Mega-Rib, non Adelanto (McElroy) | 28.8 in | 16.7 | 17 | 489.6 in |
| 5V Crimp (McElroy, MBCI, A.B. Martin) | 24 in | 20.0 | 20 | 480 in |
| 1/2 in corrugated (Western States) | 21.33 in | 22.5 | 23 | 490.6 in |
| Standing seam 18 in (McElroy 138T, MBCI LokSeam) | 18 in | 26.7 | 27 | 486 in |
| Standing seam 16 in | 16 in | 30.0 | 30 | 480 in |
| Standing seam 12 in | 12 in | 40.0 | 40 | 480 in |
The short order case is easy to see in the same table. Buy the 7/8 inch corrugated off its 39 inch overall width and 480 divided by 39 gives 12.3, so the order goes in at 13 panels. The roof needs 14. The plane finishes 34.67 inches short, which is close to three feet of open deck, and the replacement panel arrives on a separate delivery with its own freight. On the 1/2 inch corrugated the same mistake produces 19 panels against a real requirement of 23.
Waste factors: a simple gable versus hips and valleys
Waste on a metal roof is a geometry problem, not a rule of thumb. Rectangular planes waste only the rip on the final panel. Triangular and trapezoidal planes waste a wedge off every panel, because each panel meets the hip or valley at a different length and the offcut is a diagonal that fits nowhere else.
The figures below are worked by The Roofing Brief from the published coverage widths above, using a 36 inch coverage panel. They are arithmetic, not a survey, so they show the floor of what the geometry costs before any site damage, mis-cuts or offcuts that cannot be nested.
| Plane type | Example | Roof area | Panel area purchased | Over purchase |
|---|---|---|---|---|
| Rectangular gable plane | 40 ft eave by 18 ft slope | 720 sq ft | 14 panels at 3 ft by 18 ft = 756 sq ft | 5 percent |
| Hip end triangle, cut to length | 24 ft base by 12 ft slope height | 144 sq ft | 8 panels, lengths 3, 6, 9, 12, 12, 9, 6, 3 ft = 180 sq ft | 25 percent |
| Hip end triangle, stock length only | 24 ft base by 12 ft slope height | 144 sq ft | 8 panels all at 12 ft = 288 sq ft | 100 percent |
Two things follow from that table. Cutting to length matters far more on hips than on gables, because ordering a hip end in one stock length doubles the material. And a valley behaves like two hip ends facing each other, so a cross gable roof with two valleys carries the wedge penalty twice.
The offcuts are not always dead loss. On a symmetrical hip end the wedge cut from one side is the mirror of the piece needed on the other, so a crew that sequences the cuts can recover part of it. That only works if the panels arrive long enough to be cut on site and if the profile is not directional, which rules out many premium metallic and batch sensitive finishes.
Before you release the order
Coverage errors are cheap to prevent and expensive to fix, because a short order on a roll formed profile means a second production run, a second freight charge, and a colour match against a different coil lot. Five checks close almost all of the gap.
- Get net coverage in writing from the supplying plant, naming the plant, the gauge and the finish.
- Confirm whether the quoted number is overall width or coverage. If the quote only lists one width, assume it is overall until proven otherwise.
- Compute panel count per plane in inches and round up on every plane separately.
- Confirm the side lap detail and whether sealant is required at that slope. Many exposed fastener profiles drop to 1:12 only with sealant at the lap, which is covered in our guide to butyl tape sealant at the side lap.
- Order all panels for one roof from one coil lot where the finish is batch sensitive, since Western States flags several of its premium colours as directional and warns against mixing coil lots.
Slope drives which profiles are even eligible before coverage matters. Section 1507.4 of the 2024 International Building Code sets the minimum slope for lapped, nonsoldered seam metal roofs without sealant at three units vertical in 12 units horizontal, one half unit vertical in 12 with applied lap sealant, and one quarter unit vertical in 12 for standing seam systems. Manufacturer minimums are often stricter than code, as with MBCI’s 3:12 floor on 5V Crimp.
Panel width also interacts with movement. Wider panels mean fewer seams and fewer fastener rows across the roof, which changes how the assembly handles metal roof expansion and contraction. For profile by profile dimensions, see our detail pages on R-panel dimensions and gauge and corrugated metal panel sizes.
Frequently asked questions
What is the difference between metal roof panel width and coverage?
Overall width is the sheet measured edge to edge before installation. Net coverage is the finished roof width each panel adds once its side lap sits under the neighbouring panel. Panel counts must use net coverage. Western States Metal Roofing publishes 7/8 inch corrugated at 39 inches overall and 34.67 inches of roof coverage, a difference of 4.33 inches on every panel.
How wide is a standard metal roof panel?
There is no single standard. R-panel, PBR and 7.2 profiles from McElroy Metal, MBCI and Western States are typically 36 inches of net coverage. 5V Crimp from McElroy, MBCI and Gulf Coast Supply is 24 inches. Standing seam runs 12, 16 or 18 inches, with 24 inch site formed options on McElroy’s 238T.
Is corrugated metal roofing 36 inches wide?
Usually not on a roof. Western States Metal Roofing’s 7/8 inch corrugated is 39 inches overall with 34.67 inches of roof coverage in PVDF, and 37 inches overall with 32 inches of coverage in SMP. Its 1/2 inch corrugated is 26 inches overall and 21.33 inches of coverage. Confirm the figure with the specific manufacturer supplying the job.
How do I calculate how many metal roof panels I need?
Measure the eave length of each roof plane in inches, divide by the manufacturer’s net coverage figure, and round up. A 40 foot plane is 480 inches, so a 36 inch coverage panel needs 14 panels and an 18 inch standing seam needs 27. Do not subtract the side lap again, because net coverage already accounts for it.
How much waste should I add for hips and valleys?
Geometry sets the floor. A rectangular gable plane 40 feet by 18 feet at 36 inch coverage buys about 5 percent more panel than its area. A 24 foot by 12 foot hip end triangle buys about 25 percent more when every panel is cut to length, and about 100 percent more if all panels arrive at one stock length. Valleys behave like paired hip ends.
Do standing seam panels come in different widths?
Yes. McElroy Metal offers its 138T in 12, 16 and 18 inch coverage and its 238T in 16, 18 and 24 inch, with 24 inch site formed only. MBCI LokSeam comes in 12, 16 and 18 inch. Western States Western Lock is 18 inches standard with 12, 14 and 16 inch alternates and custom widths from 12 to 20 inches.
Why does the same panel profile have different coverage from different suppliers?
Profile names are trade names, not standards, so tooling and coil width vary. McElroy Metal publishes Mega-Rib 26 gauge at 36 inches of coverage from its Adelanto plant and 28.8 inches from all other locations. Western States runs 7/8 inch corrugated on different coil widths for PVDF and SMP finishes, changing coverage by 2.67 inches.