Roofing

Metal Roofing Calculator

Estimate panel count and sloped panel length for one rectangular metal-roof plane from pitch and effective coverage width.

Enter the eave width, horizontal eave-to-ridge run, pitch and usable panel coverage width. The estimate separates panel count, sloped length and material area.

Calculation and worked example reviewed 2026-11-12. See our calculation methodology.

FREE access0 signup

Roofing

Enter your measurements

US UNITS

Eave width

Horizontal eave-to-ridge run

Roof rise per 12

Effective panel coverage

Extra panel allowance

Optional: Material Price ($ / unit)

YOUR ESTIMATE

16 panels to plan14 panels before allowance

Geometric panel length 16.77 ft; add end details separately.

Roof plane 670.8 sq ft · slope factor 1.118.

Formula and example

How this calculation works

This estimator converts your entered jobsite inputs (eave width, horizontal eave-to-ridge run, roof rise per 12, effective panel coverage, extra panel allowance) into consistent US trade units, computes the exact geometric baseline first, and then applies any selected waste or order allowance so you can verify both numbers before purchasing materials.

How does the metal roofing calculator formula work?

Slope factor = √(12² + pitch²) ÷ 12; panel length = horizontal run × slope factor; panel count = ceil(eave width × 12 ÷ effective panel coverage width).

(Metal Roofing Calculator)

where:

Eave width – Entered in ft (default reference: $40 ft$ );
Horizontal eave-to-ridge run – Entered in ft (default reference: $15 ft$ );
Roof rise per 12 – Entered in in (default reference: $6 in$ );
Effective panel coverage – Entered in in (default reference: $36 in$ );
Extra panel allowance – Entered in % (default reference: $10 %$ );

The formula

Inputs to result

Slope factor = √(12² + pitch²) ÷ 12; panel length = horizontal run × slope factor; panel count = ceil(eave width × 12 ÷ effective panel coverage width).

Worked example

Check the math

A 40 ft eave, 15 ft horizontal run, 6:12 pitch and 36 in effective coverage need 14 panels. Geometric slope length is 16.77 ft per panel before overhang and end allowances.

Quick lookup chart

Metal Roof Panel Count by Eave Width (36 in vs. 24 in Coverage)

Panel counts reflect net side-lap coverage width for a single rectangular roof plane before extra waste panels.

Eave Width	36 in Exposed Fastener	24 in Standing Seam	6:12 Slope Length (15 ft Run)
24 ft eave	8 panels	12 panels	16.77 ft
30 ft eave	10 panels	15 panels	16.77 ft
40 ft eave	14 panels	20 panels	16.77 ft
50 ft eave	17 panels	25 panels	16.77 ft

Limits and field checks

Before you use this result

One rectangular plane only. Effective panel width must come from the chosen product. Add eave/ridge allowances, hips, valleys, laps, trim, fasteners and manufacturer cut lengths separately. Panel count does not include waste panels.

Always enter net effective coverage width after side rib overlap (typically 36 in for R-panel/corrugated or 16–24 in for architectural standing seam).
Add eave drip overhang (typically 1.5 to 2 in) and ridgehem/vent clearance to the geometric slope length before ordering custom-cut sheets.
Order matching ridge cap, gable rake trim, closure strips, pipe boots, and neoprene-washer screws at roughly 80 screws per roofing square.

Questions answered

Calculator FAQ

What panel width should I enter?+

Enter the manufacturer's effective coverage after side laps, not the sheet's overall physical width.

Does the result include ridge and eave overhang?+

No. It shows geometric roof-plane length; add the product-specific end allowances before ordering.