Metal Roofing Calculator

Estimate full-length panels, roof area and trim from the finished roof dimensions.

Measurement system
Roof type
Roof length along eave (ft)
Total horizontal span (ft)For a gable roof, this is the full width across both slopes.
Pitch rise per 12 in

Usable panel coverage width (in)Use the manufacturer’s coverage width after sidelap—not raw sheet width.
Extra panels allowance (%)

Optional: panel limits, trim, fasteners and cost

Maximum available panel length (ft)A warning appears if the required full length is longer.
Fasteners per panelEnter only a supplier- or engineer-approved quantity.

Trim stock

Stock piece length (ft)
End overlap per joint (in)

Panel cost

Price basis
Unit price

Full-length panels to order—

Required panel length—

Actual roof area—

Estimated panel cost—

Planning item	Result

Counts are planning estimates. Confirm panel profile, edge details, laps, fastening pattern and cut list with the manufacturer or installer before ordering.

How to calculate metal roofing panels

Measure the finished roof length along the eave, including the planned overhang.
For a gable or shed roof, enter its horizontal span and pitch. If the slope length is already known, choose the custom option.
Enter the panel’s usable coverage width from its product sheet.
Use the result as a takeoff check, then confirm full-length panel availability and trim details with the supplier.

Checked example: a 40 ft gable roof with a 24 ft span and 6:12 pitch has a slope length of 13.42 ft. With 36 in coverage, it needs 14 panels per plane, 28 base panels, or 30 panels after a 5% allowance.

Formulas used

Slope length = horizontal run × √(1 + (pitch ÷ 12)²). For a gable roof, the run is half the total span; for a shed roof, it is the full span. Panels per plane = roof length ÷ usable coverage width, rounded up. Total order panels = base panel count × (1 + allowance), rounded up. Actual roof area = roof length × slope length × number of planes.

Trim estimates

The calculator separates ridge, eave or high/low edge, and rake trim. When a trim run exceeds one stock piece, the piece count accounts for the entered end overlap. Openings, valleys, hips, transitions, sidewall flashing, endwall flashing and penetrations are not inferred from simple roof dimensions.

Important limits

Do not join short panels across the slope unless the roofing system explicitly permits that detail. This tool warns when the required panel length exceeds the maximum entered instead of inventing a horizontal lap. Wind, snow, uplift, substrate, clip spacing and fastener schedules require project-specific engineering, code compliance and manufacturer instructions.

Unknown roof slope? Use the Roof Pitch Calculator to find pitch, angle, percentage and rafter line length, then return here for metal panels and trim.