How to Calculate Metal Roof Cost — Step by Step

The six steps at a glance

Metal roof cost is the roof area times the prices, plus the old-roof removal. The six steps are: measure the length and width, pick the pitch factor, work out the roof area, add the waste, price the materials and labour, and add the removal. The worked example comes to $20,934.00 for a 40x30 ft roof, or $15.17 a square foot.

Step 1 — Measure the length and width

Measure the roof length and width in feet, on the ground. The length is measured along the eave, and the width is measured from the eave to the ridge, on the ground, not up the slope. A typical house roof is about 40 ft long and 30 ft wide. Write both numbers down: a length that is wrong by a foot makes the area wrong by a whole strip of roof. The worked example uses 40 ft by 30 ft.

Step 2 — Pick the pitch factor

Pick the pitch factor for the roof slope, because the slope adds area to the flat footprint. The pitch factor turns the flat area into the sloped area of the roof: a 4/12 pitch is about 1.05, a 6/12 pitch is about 1.12 and an 8/12 pitch is about 1.20. The worked example uses a pitch factor of 1.15.

Step 3 — Work out the roof area

Multiply the length by the width by the pitch factor: that is the roof area in square feet. For the worked example, 40 times 30 times 1.15 is 1,380.00 sq ft. That is the area of the roof itself, before any waste is added. Write the number down next to the length and width: it is the number the per-square-foot figure is divided by at the end.

Step 4 — Add the waste

Multiply the roof area by one plus the waste, as a decimal: that is the billable area, the area you pay for. For the worked example, 1,380.00 times 1.10 is 1,518.00 sq ft at 10% waste. The waste covers the cuts and offcuts, which the supplier still charges for. A simple roof with few cuts can run under 10%, and a roof with valleys, dormers or skylights needs more.

Step 5 — Price the materials and labour

Multiply the billable area by the material price a square foot, and again by the labour price a square foot. For the worked example, 1,518.00 times $9.00 is $13,662.00 of materials, and 1,518.00 times $4.00 is $6,072.00 of labour. Standing-seam panels are about $9.00 a square foot, and corrugated panels are about $5.00. About $4.00 a square foot is typical for labour, and a DIY job is $0.

Step 6 — Add the removal

Add the old-roof removal to the materials and labour: that is the total. For the worked example, $13,662.00 plus $6,072.00 plus $1,200.00 is $20,934.00. The removal is a flat figure, and about $1,200 is typical for a house roof. Divide the total by the roof area for the cost per square foot: $20,934.00 divided by 1,380.00 is $15.17 a square foot.

The worked example, line by line

Setup: 40 ft by 30 ft, pitch 1.15, material $9.00 a square foot, labour $4.00 a square foot, waste 10%, removal $1,200. Line 1, the length and width: 40 ft by 30 ft, measured on the ground. Line 2, the pitch factor: 1.15, for a medium slope. Line 3, the roof area: 40 times 30 times 1.15 is 1,380.00 sq ft. Line 4, the billable area: 1,380.00 times 1.10 is 1,518.00 sq ft. Line 5, the materials and labour: 1,518.00 times $9.00 is $13,662.00, and 1,518.00 times $4.00 is $6,072.00. Line 6, the total: $13,662.00 plus $6,072.00 plus $1,200.00 is $20,934.00, or $15.17 a square foot. Every figure here comes from the same six steps, and the metal roof cost calculator runs them for any roof you enter.

Other roofs, checked

A 30x25 ft roof: 862.50 sq ft, 948.75 sq ft billable, $13,533.75, $15.69 a square foot. Material at $12.00 a square foot: $25,488.00, $18.47 a square foot. Material at $5.00 a square foot, corrugated: $14,862.00, $10.77 a square foot. Waste at 0%: $19,140.00, $13.87 a square foot. Removal at $0: $19,734.00, $14.30 a square foot. DIY labour at $0: $14,862.00, $10.77 a square foot. A pitch of 1.30: 1,560.00 sq ft, 1,716.00 sq ft billable, $23,508.00, $15.07 a square foot. A $15,000 budget covers 965.03 sq ft, a $25,000 budget covers 1,664.34 sq ft, and a $20,934 budget covers 1,380.00 sq ft.

What the six steps leave out

The six steps count the roof, the materials, the labour and the removal, and they leave out the extras: gutters, flashing, underlayment and permits are priced separately on a real quote, and a roof with valleys, dormers or skylights needs more waste than 10%. The six steps assume the roof is a plain rectangle and the pitch factor is 1.15, and they assume the material and labour prices are per billable square foot. The six steps cannot tell you how your roof is shaped, so measure it, and check the pitch factor against the slope before you trust the area. For the insulation under the roof, see the insulation cost calculator, and for the asphalt alternative, see the asphalt calculator.