Calculate Roof Area
Free calculate roof area tool: rectangular plan, optional eave overhang, footprint vs gable deck from pitch (rise/12), illustrative hip bump, squares, and scenario rows—plus a plain-English guide. Not a professional takeoff.
Safety notice: Measuring a roof from a ladder is dangerous. Prefer ground measurements + geometry, aerial imagery with known scale, or a licensed roofer / survey. This tool is educational math for simple rectangles—not a takeoff for ordering bundles on complex hips, valleys, dormers, or curved details.
Summary: Enter a rectangular plan (length × width in feet), optional uniform eave overhang added around the plan, and a roof pitch (rise per 12" run) for sloped modes. The tool reports plan area and an estimated roof deck area for a symmetric gable model or an illustrative hip bump, then shows scenario rows—same spirit as the mortgage calculator’s stress checks.
What this tool does — and does not (tap to expand)
- Does: computes plan area from dimensions, applies a gable sloped-area factor √(1 + (rise/12)²) to the whole rectangle (valid when the ridge runs along one pair of walls and both slopes cover the full span—see methodology), and applies an approximate hip adjustment for comparison only.
- Does not: model valleys, dormers, stepped pitches, crickets, curved turrets, or waste/starter—those belong in a field measure and supplier takeoff.
Calculate roof area (planning helper)
Use Footprint only for flat or “order-of-magnitude” membrane jobs; use Gable or Hip (approx.) when you want a quick sloped-surface check before you talk to a roofer about bundles and waste.
Assumptions & methodology (short)
- Effective plan length L′ = L + 2e, width W′ = W + 2e, where e is eave overhang (feet) applied uniformly on both sides of each dimension.
- Plan area = L′ × W′ (ft²).
- Gable roof deck (simplified): deck ≈ plan area × √(1 + (P/12)²), where P is rise per 12" horizontal run. This matches two identical rectangular slopes when the ridge parallels one plan edge and each slope’s horizontal “run” is half of that span—your inputs should reflect that geometry.
- Hip (illustrative): deck ≈ gable deck × 1.09 (typical planning bump for hips; real hips vary with plan aspect ratio and truncation).
- Shingles are sold in squares (100 ft²); rounding and waste are separate from deck area.