Spike's Calculators


Gambrel Roof - Asphalt Shingles Calculator

Spike's Calculators

Calculate the amount of asphalt/fiberglass shingles needed to cover a Gambrel roof.

Gambrel style roof

As a note:

One pack of standard shingles = covers 33 sq. ft. a pack.
But with all the different types available, not all packs are equal in the amount of pieces they contain, the length of the individual shingle and the square foot coverage per pack. Not all types of shingles can be used for the starter strip and the ridge capping needed or you could be using ridge caps to cover the top ridge and the hips. That is why this calculator requires "the square foot one pack will cover" and the results for starter strip and ridge capping is in lineal feet needed for those two items and is not included in the Total Packs Needed.

Shingles Calculator

Building Length ft inch
Building Width ft inch
Eaves Overhang inch
Gable Overhang inch
Wall to Upper Pitch Start ft inch
Upper Roof Pitch /12
Lower Roof Pitch /12
Coverage of One Pack ft²
Waste %


Roof Area ft²
Ridge Length lineal ft
Shingle Starter Strip lineal ft
Shingles Needed to Cover Roof packs
Waste Factor Adds: packs
Total Shingles Needed packs


  1. Enter the length of the building. (feet+inches)
  2. Enter the width of the building. (feet+inches)
  3. Enter the overhang of the eaves. (inches)
  4. Enter the overhang of the gable. (inches)
  5. Enter the Wall to Upper Pitch Start. The length measured from the outside of the wall to where the upper slope from the Gambrel roof starts.
  6. Enter the pitch of the upper roof (rise /12")
  7. Enter the pitch of the lower roof. (rise /12")
  8. Enter the coverage of One Pack. (square feet)
  9. Enter a waste factor. (percentage)


The shingle Starter Strip amount of shingles needed is provided in lineal feet and includes a row of shingles along the rakes. The amount of shingles needed for this is not included in the Total Packs of Shingles needed.

Gambrel Roof - Asphalt Shingles Calculator
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