Free estimate — verify against local code before building
Metal Roofing Calculator
Estimate metal panels by installed width and sloped cut length, plus compatible trim, fasteners, and optional cost.
What this calculator includes
Turn a simple gable or shed roof footprint into a profile-specific metal-panel takeoff. The calculator uses installed panel coverage rather than nominal width, keeps the sloped cut length visible, and counts ridge, eave, and rake trim from separate physical runs using editable lap and trim-waste assumptions. It is intentionally different from the shingle calculator and does not select a panel system, minimum slope, clip pattern, attachment, flashing, or structural support.
Next step in your project
Verify the roof-deck sheet takeoff
Carry compatible roof dimensions into the sheathing calculator, then confirm panel orientation, clips, fasteners, waste, and deck condition.
Open Roof Sheathing Calculator →Compatible measurements are carried into the next calculator; product-specific assumptions remain editable.
How to use this metal roofing calculator
- 01
Measure the horizontal roof plan
Enter wall-line length and width plus the horizontal overhang. Do not substitute a tape measurement taken along the roof surface.
- 02
Enter pitch and roof form
Pitch converts horizontal run to panel cut length. Use gable for two equal planes or shed for one plane.
- 03
Use installed panel coverage
Copy the coverage width after sidelap or seam engagement from the selected panel documentation, not the panel's nominal sheet width.
- 04
Audit trim, fasteners, and cost
Replace trim stock length, required lap, trim waste, fastener use, package count, and prices with the approved system and current supplier quote.
Worked example
Example: 40 by 28 ft gable roof
With 1 ft overhangs, a 6-in-12 pitch, and 36 in installed panel coverage, the 42 ft ridge needs 14 panels per plane. Two planes use 28 panels before the editable spare allowance, and each panel is about 16.77 ft long along the slope.
Practical buying and overage guidance
Obtain a system takeoff and shop drawing from the selected panel supplier before ordering. Confirm usable coverage, exact order lengths, substrate, underlayment, clips or exposed fasteners, compatible metals and coatings, trim geometry, required trim laps, cut waste, closures, sealants, ventilation, delivery access, and safe panel handling. Long custom panels may require special freight and lifting plans.
Calculation sources and review
Primary references and formula assumptions are linked so you can verify them against the selected product, supplier, and adopted local requirements.
Internal formula review completed July 13, 2026. What this review covers
- Metal Construction Association - technical resources (opens in a new tab)
Industry resources for metal roof systems, profiles, accessories, and installation considerations.
- Metal Building Manufacturers Association - resources (opens in a new tab)
Metal building and roofing-system technical information; the selected manufacturer's documents remain controlling.
- OSHA - residential fall protection (opens in a new tab)
Roof work presents severe fall hazards and requires appropriate planning and protection.
Frequently asked questions
How is the number of metal roof panels calculated?
The eave or ridge run is divided by installed panel coverage and rounded up per plane. The calculator then adds the editable spare-panel percentage and rounds again to whole panels.
Why does panel cut length use roof pitch?
Panels run along the slope. The horizontal run is multiplied by the pitch factor, square root of 12 squared plus rise squared divided by 12, to estimate the sloped length.
Does this work for hip roofs or roofs with valleys?
No. Tapered hip panels, valleys, dormers, transitions, and unequal planes require a roof-specific panel layout and manufacturer takeoff. Break simple independent planes into separate estimates only when that method matches the system.
Are clips, closures, sealants, and flashing included?
Only a general fastener package and basic ridge, eave, and rake trim are estimated. Clips, closures, underlayment, ventilation, snow retention, sealants, penetration flashing, and specialty transitions are system-specific.
Why is trim lap entered separately from trim waste?
A lap reduces the installed coverage of every trim piece after the first one in an uninterrupted run. Trim waste adds whole spare pieces after ridge, eave, and rake families are counted separately. Confirm both assumptions with the selected system.
Can I order panels at the calculated cut length?
Treat it as a planning length. Confirm field dimensions, squareness, eave and ridge details, handling limits, thermal movement, and the supplier's required order length before fabrication.