Metal Roofing Calculator
Estimate metal roof panels by roof plane using installed coverage, full-length or stock sheets, end laps and spare panels. Save and download your panel schedule.
- Separate roof planes
- End-lap calculations
- Downloadable panel schedule
Metal roofing · rectangular planes
Plan your metal panels
Start with a measured roof plane. Panels run from eave toward ridge. Include required overhangs and clearances in the dimensions; do not enter floor area.
Rectangular planes only. Hips, valleys and diagonal cuts need an individual panel cut list. Fasteners, clips, trim, underlayment and structural design are excluded.
Panels to plan for
28
28 layout panels + 0 spare panels.
Measured roof surface
1,440 sq ft
Eave width × sloped run × identical planes. No waste added.
Total panel length ordered
504 linear ft
Sum of ordered sheet lengths, including laps and spares; not roof edge length.
Roofing squares
14.4
Measured sloped area ÷ 100. Panel counts use layout, not area.
Your panel schedule
Confirm supplier increments and installation allowances before ordering. Rounded display values are not cut lengths; CSV keeps calculation precision.
Main gable
28 panels × 18 ft
- Layout
- 14 across × 1 up the slope × 2 identical planes
- Allowance
- 28 layout + 0 spare panels
- Width to trim per plane
- About 2 ft across the last column; verify layout at both edges.
Each column is rounded up before multiplying by rows and repeated planes. Offcuts are not reused across groups. Full-length mode assumes the supplier can make, transport and handle the required length.
Transparent
Formula, intermediate values and rounding rules are visible.
Private by default
Saved project measurements stay in this browser unless you copy a share link.
Purchase-aware
Inputs, units and limitations stay visible so you can verify each estimate.
Count panels by layout, not just roof area
Metal panels cover strips of a roof. Divide each rectangular plane’s eave width by the panel’s installed coverage width, then round up before combining planes. A part-width strip still requires a panel, and unused width on one plane does not automatically cover a strip on another.
Installed coverage is the net width after the side lap or seam. It is not necessarily the sheet’s overall width. For example, Union Corrugating lists 36-inch coverage for MasterRib. Other profiles differ; enter the coverage from your selected product instead of treating the example as a standard.
Full-length mode uses one sheet per column, with a planning length equal to the entered sloped run. Stock mode uses equal-length sheets in multiple rows. Each joint reduces combined coverage by the end lap. Offcuts and partial last rows are not reused in this estimate.
Your dimensions must already account for the required eave projection and ridge clearance. If you import saved gable dimensions, the calculator derives two equal sloped planes from the footprint and pitch; review those dimensions before ordering. The import does not model hips, valleys or intersections.
Columns across
ceil(eave ft × 12 ÷ coverage in)Round separately for each plane width. Side lap is already included in installed coverage.
Stock rows up slope
max(1, ceil((S − O) ÷ (L − O)))S = sloped run, L = stock length, O = end lap; all in feet. L must exceed O. n rows cover nL − (n−1)O.
Order per group
base + ceil(base × spare % ÷ 100)Base = columns × rows × identical planes. Full-length mode always has one row.
How to use this calculator
- 1Split the roof into rectangular planes. Measure each plane across the eave and along the slope using existing plans or a safe measurement method.
- 2Group only identical planes. A symmetric gable commonly has two; a porch or addition may need its own group.
- 3Enter installed panel coverage from the product sheet. Choose full-length panels or a supplier’s stock length.
- 4For stock lengths, confirm that end laps are permitted for the selected system and enter the required lap. The 6-inch starting value is an example, not an installation instruction.
- 5Add optional spares, inspect each group’s schedule and download the CSV. Have the supplier confirm order lengths, handling limits and the accessory list.
Common mistakes
- • Dividing combined roof area by sheet area, which can miss a required column on each plane.
- • Entering the horizontal run as the sloped sheet length, or using the full building span for one gable side.
- • Subtracting side lap from a net coverage width a second time.
- • Using a universal end lap or minimum slope. Both depend on the selected panel system and its approved details.
- • Treating extra spares as a solution for hip or valley cuts. Diagonal panels require a cut list and layout review.
Use this calculator when
- The roof consists of rectangular planes with panels running from eave toward ridge.
- You know the net installed width and can verify the required panel lengths with a supplier.
- You want to compare full-length panels with a permitted stock-sheet layout.
Use another method when
- The roof has triangular hips, valleys, curved surfaces or penetrations requiring a detailed panel cut list.
- You need structural sizing, fastening schedules, wind or snow-load checks, or an installation design.
- You only know total roof area; area alone cannot determine the number of columns and rows.
Worked example
Two 40 ft × 18 ft planes with 36-inch coverage
Each plane needs ceil(40 ÷ 3) = 14 columns. Full-length 18-foot panels give 14 × 1 × 2 = 28 panels. With 10-foot stock and a 6-inch example end lap, two rows cover 19.5 feet, so the layout needs 56 stock sheets. Adding 5% spares to the full-length group adds ceil(28 × 0.05) = 2 panels.
Full-length: 28 panels before spares; 30 with 5% spares. Stock: 56 before spares.
Product references
- Union Corrugating — MasterRib product specifications
Reference for the example installed coverage; the page links to the current installation manual. This calculator is not affiliated with the manufacturer.
- Union Corrugating — product literature
Choose the manual for your actual panel profile. Verify laps, slope limits, lengths and trim with your supplier.