Metal Roof Cost Calculator

Background.

Suppliers quote metal roofing in several ways — per sheet, per linear metre of a given cover width, per square metre, or in North America per 'square' of 100 square feet — but whatever the quote, nobody buys exactly the area of their roof. Panels are cut to length at the eaves, trimmed at angles along hips and valleys, and overlapped where they meet, and every cut leaves an offcut that cannot go back up. A material budget therefore starts with two numbers: how big the roof surface really is, and how much extra to order.

The first trap is the area. A floor plan gives the footprint, but a pitched roof is larger than the ground it covers. On a 6-in-12 pitch every square metre of plan becomes about 1.118 square metres of roof, and on a 12-in-12 pitch about 1.414. The figure entered here has to be the sloped surface, measured on the roof or worked out from the plan and the pitch.

The second is waste. A plain gable with two rectangular planes cuts cleanly; a hipped roof with dormers and valleys produces angled scrap on panel after panel. The page adds your chosen percentage to the measured area, multiplies by the price per square metre you have been quoted, and reports both the area to buy and the material spend.

What it leaves out matters as much. Unless your unit price already includes them, ridge caps, flashings, fasteners, underlayment, delivery, tax and labour all sit on top. Read the result as the panel line of a roofing budget rather than the price of a finished roof.

What is metal roof cost calculator?

Material-only roof cost is the money spent on the roofing panels for a given roof: the area that has to be purchased once offcuts are allowed for, multiplied by the unit price. Here the purchase area is the measured sloped roof area increased by a waste percentage, and the cost is that area times the price per square metre you enter. The answer is in whatever currency your price uses; the page neither assumes nor converts a currency.

How to use this calculator.

1. 01Enter the measured roof area in square metres, taken on the slope. If you only have plan dimensions, multiply the footprint by the slope factor for your pitch — about 1.118 for 6-in-12 — or run a roof-area calculation first.
2. 02Set the waste allowance as a percentage. Long, simple gable planes need less than hipped roofs with valleys, dormers or skylights, where many panels are cut at angles. The field needs a value above zero.
3. 03Enter the material price per square metre from your supplier's quote. A price per square (100 ft²) divided by 9.290304 gives the price per m²; a price per square foot multiplied by 10.764 does the same.
4. 04Read the material-only cost alongside the area including waste, then budget trim, fasteners, underlayment, delivery, tax and labour separately unless your unit price already covers them.

The formula.

The arithmetic runs in two steps. First the purchase area, A_buy = A × (1 + w ÷ 100), where A is the measured sloped area in square metres and w is the waste allowance in percent; a 10% allowance multiplies the area by 1.10. Then the cost, C = A_buy × p, where p is the material price per square metre. Area and price are straight multipliers, so doubling either doubles the cost. Waste works on the factor 1 + w/100 rather than on the cost itself, so moving from 10% to 15% raises the cost by 5/110, about 4.5%, not by half. The input most often got wrong is the area: entering the footprint of a 6-in-12 roof instead of its sloped surface understates the area, and therefore the cost, by about 10.6%. All three inputs must be positive numbers.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Metal Construction Association, Metal Roof Installation Manual (BIBLIOGRAPHIC).
2. [2]NRCA, The NRCA Roofing Manual: Metal Panel and SPF Roof Systems (BIBLIOGRAPHIC/PAYWALL).
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.