Roof Area Calculator

A roof is always bigger than the ground it covers, and how much bigger depends only on the pitch. Measure the outside walls, add the eave overhang and choose the pitch, and this gives the sloped area in square feet and in roofing squares, the common rafter length, the ridge height and length, the gutter and rake runs, and the pitch as an angle in degrees. Hip roofs also get the corner hip rafter, and gable roofs the area of the two end walls. Two other modes work from a tape measure taken on the roof itself, or convert a rise over run reading into pitch, angle, percent slope and multiplier. It handles straight rectangular planes at one pitch, so dormers, wings and valleys have to be measured and added separately, and it stops at geometry rather than materials or cost.

Calculator Type
Measurements In
Building and roof lengths in feet, overhangs and level readings in inches, areas in square feet. The pitch itself is a ratio and reads the same either way.

Measure the outside walls, add the eave overhang, and pick the pitch.

How far in inches the roof sticks out past the wall, on each side. Blank takes 12 in, and 0 works from the walls alone.
Rise over a run of 12, which is a ratio: 6 in 12 is the same roof as 150 mm in 300. The angle and the multiplier are given beside each choice.
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Measurements In
Building and roof lengths in feet, overhangs and level readings in inches, areas in square feet. The pitch itself is a ratio and reads the same either way.

If you have measured the roof itself, or a tape up the slope, give one plane and how many of that size there are.

Eave to ridge in feet, measured on the slope and not the horizontal run.
Fill this in, in feet, to get the pitch of the plane as well. Enter 0 to leave it out.
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Measurements In
Building and roof lengths in feet, overhangs and level readings in inches, areas in square feet. The pitch itself is a ratio and reads the same either way.

Hold a level out from the roof and measure down: this converts that reading into every form of the pitch.

Inches. Rise and run only have to match each other, and 6 over 12 is how a pitch is usually quoted.
Blank takes a 12 in level, which is how pitch is usually quoted.
Square feet, or square metres in metric. Leave at zero to skip it.
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