Roof Pitch Calculator
Use this free roof pitch calculator to quickly determine the slope and angle of your roof. Enter values like rise and run to get accurate pitch results, making it easy to plan roofing materials, calculate angles, and estimate construction requirements for residential and DIY projects.
Pitch = rise per 12 inches of run · A 6/12 pitch rises 6 inches for every 12 inches of horizontal run · Roof area always exceeds footprint due to slope
How Does the Roof Pitch Calculator Work?
Roof pitch describes how steeply a roof slopes, expressed as the number of inches of vertical rise per 12 inches of horizontal run. A 6/12 pitch means the roof rises 6 inches for every 12 inches it runs horizontally. This calculator works from three input modes — rise & run, angle in degrees, or pitch notation — and calculates the pitch, angle, pitch multiplier, rafter length, and actual sloped roof area.
Knowing your roof pitch is essential for roofing material calculations. Roof shingles, metal panels, and underlayment are quoted by the actual sloped area — not the flat footprint. A 6/12 pitch roof is 11.8% larger than its footprint; a 12/12 pitch is 41% larger. Skipping the pitch multiplier is how homeowners under-order roofing materials. Use our roofing material calculator for a full shingle and underlayment count once you know your pitch.
You don't need to get on the roof to measure pitch. Place a level horizontally against the roof surface and measure 12 inches along the level. Then measure the vertical distance from the 12-inch mark down to the roof surface — that's your rise. Example: if you measure 5 inches of rise over 12 inches of run, your pitch is 5/12. You can also use a smartphone app with an inclinometer for an instant angle reading from inside the attic.
Roof Pitch Chart — All Common Pitches
| Pitch | Angle | Pitch Multiplier | Category | Common Uses |
|---|---|---|---|---|
| 1/12 | 4.8° | 1.003 | Flat | Low-slope commercial, EPDM membrane |
| 2/12 | 9.5° | 1.014 | Low | Shed roofs, low-slope residential additions |
| 3/12 | 14.0° | 1.031 | Low | Modern homes, flat-look aesthetic |
| 4/12 | 18.4° | 1.054 | Moderate | Most popular residential pitch — good balance |
| 5/12 | 22.6° | 1.083 | Moderate | Traditional ranch homes, most US regions |
| 6/12 | 26.6° | 1.118 | Moderate | Very common — good drainage, walkable |
| 7/12 | 30.3° | 1.158 | Moderate-steep | Colonial style, usable attic space |
| 8/12 | 33.7° | 1.202 | Steep | Cape Cod, Tudor style |
| 9/12 | 36.9° | 1.250 | Steep | Victorian, full attic |
| 10/12 | 39.8° | 1.302 | Steep | Steep traditional, Gothic Revival |
| 12/12 | 45.0° | 1.414 | Very steep | 45° perfect diagonal — dramatic appearance |
Pitch Multiplier & Actual Roof Area
The pitch multiplier converts your roof's flat footprint into the actual sloped surface area. Roofing materials — shingles, metal panels, underlayment, ice-and-water shield — must cover the sloped surface, not the flat footprint. Using footprint area alone will cause you to under-order materials significantly on steeper roofs.
Example: 30 × 40 ft house (1,200 sq ft footprint) with 6/12 pitch:
1,200 × 1.118 = 1,342 sq ft actual roof area
1,342 ÷ 100 = 13.42 squares of roofing material needed
Roofing is sold in "squares" — 1 square = 100 sq ft of actual sloped roof area. Never use floor plan area or footprint to calculate shingle quantities. A 4/12 pitch adds ~5% to your footprint; a 12/12 pitch adds 41%. Use our roofing material calculator to get a complete shingle, underlayment, and ridge cap count based on your actual roof dimensions and pitch.
Pitch & Roofing Material Compatibility Guide
Not every roofing material works at every pitch. Using the wrong material for your pitch leads to leaks, voided warranties, and premature failure.
| Material | Min Pitch | Ideal Pitch Range | Notes |
|---|---|---|---|
| EPDM / TPO Membrane | 0/12 (flat) | 0–2/12 | Commercial flat roofs — requires proper drainage |
| Built-up Roofing (BUR) | 0/12 | 0–3/12 | Gravel-topped, low-slope commercial |
| Modified Bitumen | 0.25/12 | 0–4/12 | Torch-applied low-slope membrane |
| Metal Roofing (standing seam) | 0.5/12 | 0.5/12+ | Works on near-flat to very steep — most versatile |
| Asphalt Shingles (3-tab) | 2/12 | 4–9/12 | Most common — requires 2× underlayment below 4/12 |
| Architectural / Dimensional Shingles | 2/12 | 4–12/12 | Most popular residential — 30–50 year lifespan |
| Wood Shakes / Shingles | 3/12 | 4–12/12 | Requires breathing gap; not for low pitches |
| Slate | 4/12 | 6–12/12 | Heavy — verify structural support; 75–150 yr lifespan |
| Concrete / Clay Tile | 4/12 | 5–12/12 | Very heavy — requires engineered support |
Example Calculations
Example 1 — Finding Pitch from Rise & Run
Pitch = 7/12
Angle = arctan(7 ÷ 12) = 30.3°
Pitch multiplier = √(1 + (7/12)²) = 1.158
Example 2 — Calculating Actual Roof Area
Footprint = 28 × 45 = 1,260 sq ft
Run = 28 ÷ 2 = 14 ft per side
Rafter length = √(14² + 7²) = √(196 + 49) = √245 = 15.65 ft
Actual roof area = 1,260 × 1.118 = 1,409 sq ft = 14.09 squares
Example 3 — Converting Angle to Pitch
Rise = tan(22.6°) × 12 = 0.4163 × 12 = 5 inches → 5/12 pitch
Pitch multiplier = 1.083