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CalcTheBuild

Roofing Calculator

Get a quick estimate for a new roof without climbing a ladder. Enter the house footprint, the eave overhang and the roof pitch to get the true roof area, shingle bundles, underlayment and the installed cost.

ft
ft
in
%

10% for simple gables, 15% for hips and valleys.

$/sq ft

Material + labour per unit of roof area.

Your estimate

Roof area (with waste)
1,653 sq ft
Estimated installed cost
$7,513
Actual roof surface
1,503 sq ft
Roofing squares
16.5 squares
Shingle bundles (3 per square)
50 bundles
Synthetic underlayment rolls
2 rolls
Pitch multiplier
1.118

Assumes a simple roof with one pitch. Add ridge cap and starter strip separately.

How to use this calculator

  1. Measure the length and width of the house at ground level.
  2. Enter the eave overhang, typically 12–24″ (300–600 mm).
  3. Choose the roof pitch (rise per 12 units of run). Most homes are between 4/12 and 9/12.
  4. Add 10% waste for simple gable roofs and 15% for hip roofs or roofs with valleys and dormers.
  5. Enter an installed price per square foot or square metre to estimate the total cost.

How roof area is calculated

The footprint plus overhangs gives the roof's plan area. A sloped roof covers more surface than its plan area, so we multiply by the pitch factor √(1 + (rise ÷ 12)²). A 6/12 roof has a factor of 1.118, meaning 11.8% more area than the flat footprint.

In North America roofing is sold by the 'square' (100 sq ft). Standard architectural shingles come three bundles to the square.

Pro tips

  • Get at least three written quotes, and check that tear-off, disposal and flashing are included.
  • Steep roofs (above 8/12) usually cost more per square to install because of extra safety equipment and slower work.
  • Ice and water shield is required along eaves in cold climates. Budget for it separately.

Frequently asked questions

What is a roofing square?

A roofing square is 100 square feet (9.29 m²) of roof surface. A typical 2,000 sq ft house has about 20–30 squares of roof.

How many bundles of shingles per square?

Most three-tab and architectural asphalt shingles come three bundles per square. Some heavy designer shingles need four or five.

How much does a new roof cost?

In the US, an asphalt shingle roof typically costs $4.50–$7 per sq ft installed. Metal, tile and slate cost considerably more.

These results are estimates for planning and budgeting. Actual quantities depend on site conditions, products and workmanship. Check structural and code requirements with a licensed professional before you build.