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Roofing calculator

Estimate roof surface, squares, shingle bundles, felt rolls and cost.

Get started

  1. Choose footprint and pitch or angle. Use measured length and width for a rectangular footprint.
  2. For a complex roof, add measured sloped sections and enter their total in Known roof area.

Example

Input

2,000 ft² footprint, 6/12 pitch, 1 ft overhang.

Expected result

About 2,461 ft², 28 roofing squares with 10% allowance.

Try it

Good to know

The calculation runs in your browser. Use consistent units in fields with no explicit unit.

Calculation method

With footprint alone, the overhang estimate uses A + 4.4e(√A + e), where e is horizontal overhang. With measured rectangular sides, use (l + 2e)(w + 2e). Apply the slope factor to that horizontal area. One roofing square is 100 ft². Counts use typical US coverage; check product specifications.

Aproj≈A+4.4e(A+e),Arect=(l+2e)(w+2e)A_{\rm proj}\approx A+4.4e(\sqrt A+e),\qquad A_{\rm rect}=(l+2e)(w+2e)
Aroof=Aproj1+(p/12)2=Aprojcos⁡θ,Nsquares=⌈Aroof,ft2(1+a/100)100⌉A_{\rm roof}=A_{\rm proj}\sqrt{1+(p/12)^2}=\frac{A_{\rm proj}}{\cos\theta},\quad N_{\rm squares}=\left\lceil\frac{A_{\rm roof,ft^2}(1+a/100)}{100}\right\rceil

Calculation mode

Footprint and pitch
  • Footprint area
  • Area unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Rise per 12 horizontal
  • Horizontal overhang
  • Overhang unit · mm / cm / m / in / ft / yd
  • Unit price
  • Price unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Waste allowance · %
Footprint and angle
  • Footprint area
  • Area unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Roof angle · °
  • Horizontal overhang
  • Overhang unit · mm / cm / m / in / ft / yd
  • Unit price
  • Price unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Waste allowance · %
Known roof area
  • Roof area
  • Area unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Unit price
  • Price unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Waste allowance · %
Measured length and width
  • Length
  • Length unit · mm / cm / m / in / ft / yd
  • Width
  • Width unit · mm / cm / m / in / ft / yd
  • Rise per 12 horizontal
  • Horizontal overhang
  • Overhang unit · mm / cm / m / in / ft / yd
  • Unit price
  • Price unit · cm² / m² / in² / ft² / yd² / acre / ha
  • Waste allowance · %