Mathematics is the queen of the sciences.C. F. Gauss

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Roofing & rafter calculator

Roof area, pitch geometry, rafter length and material quantities.

6

Enter known values

Fill in the fields below — the result will appear alongside.

Live construction diagram
lᵣW = 0 ftα = 0 °
Gable roof
Roof tiles
ft
ft
degree
in
in
ft2

Formulas

Ap=(L+2e)(W+2e)A_p=(L+2e)(W+2e)r=W/2+er=W/2+er=W+2er=W+2eh=rtan⁡(α)h=r\tan(\alpha)lr=r/cos⁡(α)l_r=r/\cos(\alpha)A=2(L+2e)lrA=2(L+2e)l_rA=(L+2e)lrA=(L+2e)l_rAt=A(1+w/100)A_t=A(1+w/100)Nr=2(⌈(L+2e)/s⌉+1)N_r=2(\lceil(L+2e)/s\rceil+1)Nr=⌈(L+2e)/s⌉+1N_r=\lceil(L+2e)/s\rceil+1Nm=⌈At/Au⌉N_m=\lceil A_t/A_u\rceilLridge=L+2eL_{ridge}=L+2eLridge=0L_{ridge}=0

How it works

Calculate gable or shed roof geometry, surface area, waste allowance, rafter length and count, ridge length and roofing units by effective coverage.

The roof run and pitch determine rise and rafter length. Surface area follows the selected roof type; material quantity uses the effective installed coverage supplied by the manufacturer.

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