Quick answer: Divide your roof area by one panel's coverage (width × length minus overlap) and add ~10% for trim and waste. Plan about 80 screws per square (100 sq ft).
Calculate exactly how many metal panels, screws, and materials you need for your standing seam or corrugated roof project.
Metal roofing is not figured the way shingles are. Shingles are sold by the square (100 sq ft) and you can order area. Metal is sold as panels of a specific length and a specific coverage width, so what you actually need is a panel count and a panel length — and you cannot get either one from square footage alone.
Here is the sequence. The calculator above does all five steps, but if you want to check it or work it by hand, this is the method.
Measure the building's length (along the eave) and width, at ground level. You do not need to get on the roof for this.
The sloped surface is always larger than the footprint. Multiply by the pitch multiplier from our roof pitch chart — 1.054 at 4:12, 1.118 at 6:12, 1.202 at 8:12.
Panel length is the rafter length plus your eave overhang. For a gable roof: (width ÷ 2) × multiplier + overhang. Round up to a stock length — panels are cut to order or sold in fixed lengths, and a panel one inch short is scrap.
This is the step people get wrong. Use coverage width, not panel width. A 36-inch corrugated panel is physically wider than 36 inches; 36 inches is what it covers after the side lap. Ordering off the physical width leaves you short.
Panels per side = eave length ÷ coverage width, rounded up. Then double it for both sides of a gable.
Panels are typically 60–70% of the order. Ridge cap, eave and rake trim, valley flashing, foam closure strips, and screws make up the rest, and they are the parts most often forgotten until the job stops.
Coverage width determines your panel count more than anything else. These are typical figures — always confirm against the spec sheet for the exact profile you are buying, because coverage varies between manufacturers even for the same nominal panel.
| Panel type | Typical coverage | Panels per 100 ft of eave |
|---|---|---|
| Corrugated / R-panel / ribbed | 36 in (3 ft) | 34 |
| 5V crimp | 24 in (2 ft) | 50 |
| Standing seam (wide) | 18 in | 67 |
| Standing seam (standard) | 16 in | 75 |
| Standing seam (narrow) | 12 in | 100 |
Narrower panels mean more panels, more seams, and more labour — but also a more refined appearance, which is why 12 and 16 inch standing seam is specified on higher-end work.
A full takeoff, so you can check the calculator against your own arithmetic.
Note what happens with the panel length: you need 17 ft 3 in and must buy 18 ft, so every panel carries about 9 inches of waste. That is normal and unavoidable with fixed stock lengths — but it is also why custom-cut-to-length panels are worth pricing on a large roof.
Installing a metal roof is one of the best investments you can make for your home, but ordering the wrong amount of panels or screws can cause massive delays. Unlike asphalt shingles that come in "squares," metal roofing is calculated by the linear foot and panel width.
Our metal roof panel calculator takes your roof's footprint, applies the correct pitch multiplier, and divides it by the exact exposure width of your chosen metal panels to tell you exactly how many sheets to buy.
The most common question DIYers have is how to calculate screws for metal roofing. The general rule of thumb for metal roofing screws (with neoprene washers) is:
Our calculator automatically calculates the total square footage of your roof and multiplies it by 1.2 to give you the exact number of screws needed, including a 20% buffer for side-laps, eaves, ridges, and mistakes.
One of the biggest advantages of metal roofing is that it can be installed on much lower slopes than asphalt shingles. However, you must follow the manufacturer's guidelines to prevent leaks:
The cost of a metal roof varies wildly based on the type of metal and the finish. On average, expect to pay:
Use the "Material Cost per Sq Ft" input in our calculator above to get an accurate estimate for your specific project.
Figuring metal roofing is a different exercise from figuring shingles, because panels come in fixed widths and custom lengths rather than bundles. Four numbers determine the whole order:
| Exposed fastener (corrugated / R-panel) | Standing seam | |
|---|---|---|
| Installed cost | Lower | Roughly 2× higher |
| Fasteners | Through the panel face | Hidden clips |
| Maintenance | Washers need replacing at 10–20 years | Effectively none |
| Expansion | Restrained by the screws | Clips allow the panel to float |
| Typical life | 25–40 years | 40–70 years |
The exposed-fastener washer cycle is the deciding factor on long runs. Every screw is a penetration with a rubber washer that eventually hardens, and on a large roof that is a real re-fastening job somewhere around year fifteen.
Yes, absolutely. You should always install a high-quality synthetic roofing underlayment (or at least #30 felt paper) over the roof decking before installing metal panels. This provides a secondary water barrier and prevents condensation from dripping onto your wood decking.
A hip roof requires more cutting and waste than a standard gable roof. Calculate your total adjusted square footage using our calculator, and then add an extra 15% waste factor to your panel order to account for the complex hip and valley cuts.
In many jurisdictions, you can install a metal roof directly over one layer of existing asphalt shingles (known as a "re-roof"). However, you must install wooden strapping (battens) horizontally over the shingles first to create a flat, ventilated surface for the metal panels to attach to. Always check your local building codes first.
Every constant this calculator uses and where it comes from, so you can check it rather than take our word for it.
Local codes amend the model IRC and adopt different cycles — your building department governs. Manufacturers revise yields; where your product's data sheet disagrees with a default here, use the product's number. See our full methodology.