Roof Pitch Explained
Roof pitch is the number of inches a roof rises for every 12 inches of horizontal run. A 6/12 roof rises 6 inches per foot. Steeper roofs have more surface area — a 6/12 roof is about 12% larger than its footprint, a 12/12 roof about 41% larger.
Pitch multiplier chart
| Pitch | Angle | Multiplier | Roof area per 1,000 sq ft footprint |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | 1,014 sq ft |
| 3/12 | 14° | 1.031 | 1,031 sq ft |
| 4/12 | 18.4° | 1.054 | 1,054 sq ft |
| 5/12 | 22.6° | 1.083 | 1,083 sq ft |
| 6/12 | 26.6° | 1.118 | 1,118 sq ft |
| 7/12 | 30.3° | 1.158 | 1,158 sq ft |
| 8/12 | 33.7° | 1.202 | 1,202 sq ft |
| 9/12 | 36.9° | 1.25 | 1,250 sq ft |
| 10/12 | 39.8° | 1.302 | 1,302 sq ft |
| 12/12 | 45° | 1.414 | 1,414 sq ft |
The multiplier is √(1 + (rise ÷ 12)²). Multiply your footprint (including overhangs) by it to get roof area.
How to measure your pitch
- From the attic: hold a level horizontally against a rafter, mark 12 inches along the level, and measure straight up to the rafter. That number is the rise.
- From a ladder at the gable: the same method works on the roof edge or a rake board.
- From the ground: smartphone pitch apps give a usable estimate.
Why pitch matters
Pitch affects how much material you buy, which roofing materials are allowed (asphalt shingles generally need at least 2/12, with extra underlayment below 4/12), and labor cost — crews need extra safety equipment on steep roofs. The roofing calculator applies the multiplier for you.