Estimate roof area from horizontal dimensions and pitch, or enter measured roof sections. Include a waste allowance and optionally calculate material packs and roofing material cost.
Choose your measurement method, enter each roof section, and calculate the area. Add material coverage or pricing when you need a purchase estimate.
Select Horizontal footprint + roof pitch for projected dimensions. If you already have measurements along the roof surface, choose a measured rectangular, triangular, or trapezoidal plane. Use Enter actual roof area for an area already adjusted for slope.
Select the unit beside each dimension before entering its value. In footprint mode, include the horizontal extent of overhangs and enter the rise per 12 units of run. Use Add Another Section for different pitches or shapes, and count each area once.
Adjust the waste allowance for your material and layout. Open Estimate material packs and enter the product’s installed coverage after overlaps. Add an optional price per area or pack. A price per pack also requires its coverage.
Select Calculate Roofing to see net roof area, area including waste, and roofing squares. Review the section breakdown and any pack or cost estimate. Recalculate after changing inputs, or select Clear All to start again.
Avoid applying slope twice: Pitch is used only with horizontal footprints. Measured roof planes already include slope. For a simple gable roof with equal pitches, enter the full footprint once rather than doubling it for the two roof faces.
See how horizontal footprint and roof pitch determine surface area, then add a waste allowance to estimate material coverage.
This example uses a simple gable roof with equal 6/12 pitches and a 10% waste allowance. The footprint includes the horizontal extent of overhangs.
Approximately 137.11 m². This includes both roof faces; do not double the result.
Use this formula when the measured footprint is horizontal and the included roof surfaces share the same pitch.
Horizontal footprint area
× √(1 + (Pitch ÷ 12)²)
The calculator uses the unrounded slope factor. Values shown in this example are rounded for readability. The 10% allowance is an example input, not a fixed requirement for every roof.
Different pitches need separate calculations: Divide a roof with varying pitches into non-overlapping projected sections, or enter the actual measured roof planes. Do not apply a pitch factor to dimensions already measured along the sloped surface.
Use your roof area estimate to plan material quantities, account for cutting waste, and understand what your material budget includes.
Enter the installed coverage stated for your chosen bundle, panel, box, or roll. Products can cover different areas, so use the manufacturer’s specifications rather than assuming every pack covers the same amount.
Cutting around valleys, hips, dormers, and roof edges can increase material waste. Adjust the allowance to suit your roof layout, material, and installation plan. The calculator’s default is a starting value you can change.
Roof covering area does not determine every accessory quantity. Starter strips, ridge caps, flashing, drip edges, fasteners, and ventilation products need their own measurements and product requirements.
Choose a price per roofing square, square foot, square meter, or pack to match your supplier’s quote. Area pricing uses the total area with waste; pack pricing uses the rounded whole-pack quantity.
Find answers about roof measurements, pitch, roofing squares, material coverage, and cost estimates.
Choose the method that matches your measurements. For a horizontal roof footprint, enter its length, width, and pitch. For measured roof surfaces, enter each section’s dimensions along the roof plane. You can also enter an actual roof area directly if you already know it.
A 6/12 pitch means the roof rises 6 units for every 12 units of horizontal run. Select 6/12 or enter 6 in the pitch field. Pitch increases the surface area calculated from a horizontal footprint; it is not entered as an angle in degrees.
For a simple gable roof with the same pitch on both sides, enter the full horizontal roof footprint once. The pitch adjustment accounts for both roof faces. If you measure the sloping roof surfaces instead, add each face separately using the measured section method.
Yes. Divide the roof into rectangular, triangular, or trapezoidal surfaces and enter their measured dimensions along each roof plane. For footprint calculations, separate areas with different pitches into non-overlapping rectangular sections and use the correct pitch for each. Each part of the roof should be counted only once.
Yes, include the roof area extending beyond the exterior walls. Horizontal footprint dimensions should include the horizontal projection of these overhangs. Measured surface dimensions should extend to the roof edges. Interior floor dimensions alone may leave out part of the roof.
One roofing square equals 100 square feet, or approximately 9.29 square meters. Divide square footage by 100 to convert it to roofing squares. The calculator’s roofing squares result includes your selected waste allowance.
The calculator starts with a 10% allowance, which you can change. The amount needed depends on roof shape, cutting patterns, and the selected material. Valleys, hips, and dormers can increase cutting waste. Confirm the allowance with your installer and enter the base roof area without waste to avoid adding it twice.
Enable the material pack option and enter the installed coverage per pack in the matching area unit. The calculator divides the area with waste by that coverage and rounds up to whole packs. For panels and rolls, use coverage after required overlaps. Panel counts remain an area-based estimate; panel lengths and the cutting layout may change the final order.
The cost result covers the selected roofing material using your entered price. Area pricing includes the waste allowance, while pack pricing uses the rounded pack quantity. Labor, tear-off, disposal, delivery, taxes, accessories, and deck repairs need to be budgeted separately.
Yes. Select the correct unit beside each dimension, including feet, inches, yards, meters, centimeters, or millimeters. The calculator converts those measurements before combining the areas. Changing a unit selection does not convert the number already entered, so check both the value and its unit.
Have your roof measurements ready? Estimate the area, add a waste allowance, and use your product coverage and prices to plan material quantities and costs.
Use the Roofing Calculator