Gable Roof Calculator
Calculate gable roof area, rafter lengths, and material quantities from building span and pitch. Includes both slopes, waste, and overhang. Free, no signup.
Roof Area Calculator
Calculate actual roof surface area from plan dimensions and pitch
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Gable roofs — did you know?
How a gable roof works
A gable roof has two slopes meeting at a central ridge. Each slope is a simple rectangle. Total roof area = 2 × (run ÷ cos(pitch°)) × building_length. At 35°, 4m run, 10m building: 2 × 4.88 × 10 = 97.6 m².
Gable vs hip — which costs less?
Gable roofs are simpler and cheaper: fewer rafters, no compound cuts, less waste (10% vs 15-20% for hips). Gable roofs also have better loft space. But they are less wind-resistant than hip roofs.
Rafter count for a gable roof
Rafters at 400mm centres: building_length ÷ 0.4 + 1 pairs. For 10m building: 26 pairs = 52 rafters. At 600mm centres: 18 pairs = 36 rafters. Add 2 for gable ladder overhangs.
Gable end area calculation
Gable triangle area = run × (run × tan(pitch°)) ÷ 2. At 4m run and 35°: 4 × (4 × 0.700) ÷ 2 = 5.6 m² per gable. Used for wall material and vent calculations.
Formulas used
Total roof area
area = 2 × (run ÷ cos(pitch°)) × length
Rafter length
rafter = run ÷ cos(pitch°)
Rafter pairs
pairs = ceil(length ÷ spacing) + 1
Gable end area
gable = run × run × tan(pitch°) ÷ 2
Frequently asked questions
How do I calculate gable roof area?
2 × (run ÷ cos(pitch°)) × building_length. At 35°, 4m run, 10m building: 2 × 4.88 × 10 = 97.6 m².
How many rafters for a gable roof?
At 400mm centres: length ÷ 0.4 + 1 pairs. 10m building = 26 pairs = 52 rafters. Add 2 for gable ladders.
Gable vs hip roof cost?
Gable is simpler: fewer rafters, no compound cuts, 10% waste vs 15-20% for hip. Gable is typically 20-30% cheaper.
Best free gable roof calculator?
One that handles both slopes, rafter counts, and material quantities. This tool does all, free.