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Roofing Calculator

Roof area, roofing squares, shingle bundles, nails, underlayment and drip edge, from the footprint and the pitch.

Roof
sq ft
The house footprint plus the overhangs (eaves and rakes), measured flat.
in 12
Inches of rise per 12 in of run. Not sure? Use the roof pitch calculator.
%
About 10% for a simple gable roof; 15% or more for hips, valleys and dormers.
Shingles
Shingles
Nails per shingle
Some local codes and high-wind areas require 6. Follow the instructions on the bundle.
Edges
Edges
ft
ft
All the roof's outside edges, for drip edge.
sq ft
Printed on the roll. Synthetic rolls often cover far more than felt.
Your price
Your price
$
Leave at 0 to skip the cost estimate.
Shingle bundles 57 bundles 1,677.1 sq ft of roof (18.45 squares with extra) at a 6/12 pitch.

Roof

Roofing squares (with extra)
18.45 squares
Actual roof area
1,677.1 sq ft
Pitch multiplier
1.118 ×

Materials

Roofing nails
4,723 nails
Underlayment
2 rolls
Drip edge, 10 ft pieces
16 pieces
Ridge cap
40 linear ft

Cost

How many bundles of shingles do I need?

Multiply the flat area under the roof by the pitch multiplier (1.118 for a 6/12 roof) to get the real roof area, add about 10% for cuts, and divide by 100 for squares. Most architectural shingles come 3 bundles to a square. A 1,500 sq ft footprint at 6/12 is 1,677.1 sq ft of roof: 18.45 squares with extra, or 57 bundles.

Worked example: a 1,500 sq ft house with a 6/12 roof

  1. Roof area: 1,500 × 1.118 = 1,677.1 sq ft.
  2. Extra: +10% for cuts, starter rows and waste = 18.45 squares.
  3. Bundles: GAF Timberline HDZ covers 98.4 sq ft per 3 bundles, so 57 bundles.
  4. Nails: 64 shingles per square × 4 nails = 256 per square: about 4,723 nails.
  5. Edges: 16 pieces of 10 ft drip edge for 160 ft of eaves and rakes, and 40 ft of ridge cap.

Bundles by footprint and pitch

With 10% extra and 3 bundles per 98.4 sq ft.

Footprint4/126/128/12
1,000 sq ft363841
1,500 sq ft545761
2,000 sq ft717581
2,500 sq ft8994101

What is a roofing square?

Roofers measure in squares: 100 sq ft of actual roof surface. A steep roof has much more surface than the floor plan suggests. A 12/12 roof has about 41% more than its footprint, which is why the pitch matters as much as the size of the house.

Other materials on the list

  • Underlayment goes under the shingles over the whole deck. Roll coverage varies a lot, so use the number on the roll.
  • Ice and water barrier is often required along the eaves and in valleys in cold climates; check local code.
  • Starter strip runs along the eaves (and often the rakes) under the first row of shingles.
  • Drip edge protects the roof edges and is sold in 10 ft lengths.
  • Ridge cap shingles cover the ridge and hips. Check the coverage per bundle of the ridge cap you choose.

Before you order

  • Check the slope: GAF requires at least 2:12 for its shingles.
  • Read the bundle wrapper. Coverage per bundle and the nailing pattern vary by product; some local codes require 6 nails per shingle.
  • Tear-off: removing old shingles adds dumpster and disposal costs; ask your roofer.
  • Measuring a roof is dangerous. Measure the footprint from the ground and use the pitch multiplier instead of climbing up.

Frequently asked questions

How many bundles of shingles are in a square?
Usually 3 for architectural shingles. GAF Timberline HDZ, for example, covers 98.4 sq ft with 3 bundles.
How many squares is a 2,000 sq ft roof?
20 squares of actual roof area, or about 22 with 10% extra. Remember that a 2,000 sq ft house has more than 2,000 sq ft of roof once you allow for pitch and overhangs.
How do I calculate roof area from the house size?
Multiply the footprint, including overhangs, by the pitch multiplier: √(1 + (pitch ÷ 12)²). For a 6/12 roof that's 1.118.
How many nails per square of shingles?
About 256 with 4 nails per shingle (64 shingles per square), or 384 with 6 nails where codes require it (GAF).
How much extra shingle should I buy?
About 10% for a simple gable roof and 15% or more for roofs with hips, valleys and dormers.

Guides

Related calculators

Roof Pitch CalculatorRoof pitch as X in 12, the angle in degrees, slope percent and roof area.Square Footage CalculatorSquare feet of any room or area, in sq ft, sq yd, m² and acres.Stair CalculatorRisers, treads, total run and stringer length, checked against the residential code.Deck CalculatorDeck boards, joists and screws or hidden fasteners for any deck size.

Sources and method

Last checked October 12, 2026. How we build and test every calculator: methodology.