以下のガイドはまだ日本語に翻訳されていないため、英語で表示しています。計算機自体はすべて日本語に対応しています。
この計算機の使い方
- Measure the outside length and width of the building.
- Enter the overhang (eave and rake extension) and the roof pitch (rise in inches per 12 inches of run).
- Add a waste allowance: about 10% for simple gable roofs, 15% or more for hip roofs and roofs with valleys or dormers.
計算式
A sloped roof covers more area than the floor below it. The pitch factor converts plan (horizontal) area into sloped area. A roofing square is 100 ft², and standard asphalt shingles come about three bundles per square.
Pitch factor = √(1 + (rise/12)²)
Roof area = (L + 2·overhang) × (W + 2·overhang) × pitch factor
Squares = area ÷ 100 ft²; bundles ≈ squares × 3
Example
- 40 × 30 ft house with 1 ft overhang: plan area 42 × 32 = 1,344 ft².
- 6/12 pitch factor = 1.118 → 1,503 ft²; +10% waste = 1,653 ft².
- 16.5 squares → 50 bundles.
よくある質問
How do I find my roof pitch?
Measure the vertical rise over 12 inches of horizontal run, with a level and tape on the roof or in the attic. A 6/12 roof rises 6 in per foot (about 26.6°).
Does this work for complex roofs?
For roofs with multiple sections or pitches, calculate each section separately and add them up. Valleys, hips and dormers need extra waste.
Do I need extra materials?
Yes: starter strips, ridge caps, underlayment, drip edge, flashing and nails are estimated separately. Check the shingle manufacturer's coverage.