Felo
Roof Pitch Calculator Free — Slope & Rafter Length
What is Roof Pitch Calculator Free?
Roof Pitch Calculator Free — Slope & Rafter Length converts roof pitch into usable numbers: rise/run ratio, angle, slope percentage, pitch multiplier, rafter length, walkability, and roof area. Enter 6/12, an angle, a percent slope, or rise and run — the agent returns the conversion, material band, and formulas.
Every value in this diagram — pitch, angle, slope percent, multiplier, and walkability — is exactly what the agent returns for a 6/12 roof.
Key Features
- Convert every pitch format — 6/12, 26.57°, 50% slope, or rise and run normalize to pitch, degrees, and slope percent.
- Calculate rafter length and roof area — uses your span or run, then converts footprint to sloped area, squares, and shingle bundles.
- Rate walkability — labels the pitch walkable, caution, or fall-protection required.
- Recommend materials by pitch — shows which roofing systems suit flat, low, standard, and steep roofs.
- Generate a labeled diagram — a clean schematic showing rise, run, rafter, angle, and slope.
How to Use
- Type the pitch you know: 6/12, 30 degrees, 50%, or "rise 3 ft, run 8 ft".
- Add the span or run for rafter length; add footprint for roof area and materials.
- Ask a follow-up such as "what roof pitch is walkable?" or "can I shingle a 3/12 roof?"
How to Measure Roof Pitch
You do not need an angle finder — a level, a tape measure, and one 12-inch mark are enough. The agent handles the trigonometry.
- Place a level 12 inches horizontally from the roof edge and mark the point.
- Measure vertically from that mark to the roof surface — this is the rise.
- Rise over 12 is your pitch: 6 inches = 6/12. For any other run, divide rise by run and multiply by 12.
Pitch, Angle, and Slope
The same roof is described three ways. A 6/12 roof rises 6 inches per 12 inches of run, which is 26.57° and a 50% slope. Builders quote pitch, inspectors and solar designers often quote angle, and roofing manufacturers quote slope. The multiplier — 1.1180 at 6/12 — turns a flat footprint into sloped roof area. Give the agent any one of the three and it returns the other two.
Roof Pitch Chart
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.33% | 1.0035 |
| 2/12 | 9.46° | 16.67% | 1.0138 |
| 3/12 | 14.04° | 25.00% | 1.0308 |
| 4/12 | 18.43° | 33.33% | 1.0541 |
| 5/12 | 22.62° | 41.67% | 1.0833 |
| 6/12 | 26.57° | 50.00% | 1.1180 |
| 7/12 | 30.26° | 58.33% | 1.1577 |
| 8/12 | 33.69° | 66.67% | 1.2019 |
| 9/12 | 36.87° | 75.00% | 1.2500 |
| 10/12 | 39.81° | 83.33% | 1.3017 |
| 11/12 | 42.51° | 91.67% | 1.3566 |
| 12/12 | 45.00° | 100.00% | 1.4142 |
Walkability & Materials by Pitch
Four pitch bands decide what a roof is usually made of and whether it is safe to walk.
| Pitch | Angle | Walkability | Common roofing |
|---|---|---|---|
| 0–2/12 | 0°–9.5° | Walkable with caution | EPDM, TPO, modified bitumen, built-up |
| 2/12–4/12 | 9.5°–18.4° | Walkable with caution | Low-slope-rated shingles over membrane, standing-seam metal |
| 4/12–6/12 | 18.4°–26.6° | Walkable with normal caution | Asphalt shingles, metal, tile |
| 7/12–8/12 | 30.3°–33.7° | Experienced only | Asphalt shingles, metal, tile |
| 9/12+ | 36.9°+ | Fall protection required | All common steep-slope materials |
Why Roof Pitch Matters
- Drainage — most shingle warranties require at least 2/12; below that you need a membrane or flat-roof system.
- Material choice — each roofing system lists a minimum slope, so the pitch narrows the shopping list before you price anything.
- Safety and cost — anything 9/12 and steeper needs fall protection, which raises labor on re-roofs and inspections.
Example Use Cases
- Shed roof planning — "I'm building a 10×12 shed with a 4/12 lean-to roof. What's the angle and rafter length?" It returns 18.43° and a 12.65 ft rafter over a 12 ft run.
- Re-roof estimate — "8/12 roof, 1,800 sq ft footprint — how many squares?" It returns 33.69°, a 1.2019 multiplier, 2,163 sq ft and 21.6 squares.
- Converting inspection notes — "The inspector wrote 9/12. What is that in degrees and slope percent?" It returns 36.87°, 75%, and a fall-protection warning.
Tips for Best Results
- Add the span for rafter length; add the footprint for roof area and materials.
- State units and whether the span is the full building width or the half-span.
- Treat walkability and code notes as general guidance.
FAQ
What input formats are supported?
Ratios (6/12), degrees, percent slope, rise per foot or metre, and separate rise and run.
How accurate are the results?
Pitch, angle, slope, and multiplier use trigonometry, rounded to two decimals. Rafter and area results depend on your span; assumptions are listed.
What pitch is 30 degrees?
30° is about 7/12: tan(30°) × 12 ≈ 6.93. The agent converts both ways.
What is the roof pitch multiplier?
√(1 + (pitch/12)²) × footprint. It converts flat area to sloped roof area.
Can you shingle a 3/12 roof?
Yes, with low-slope-rated shingles over an underlayment or membrane. Confirm the manufacturer's rating.
What roof pitch is walkable?
0–6/12 is walkable, 7/12–8/12 is for experienced workers, and 9/12+ needs fall protection. Verify on site.
How does Roof Pitch Calculator Free compare to Omni Calculator?
Those are form-based: fill a field, get one number. This agent takes natural language and continues into rafter length, roof area, walkability, and materials in one conversation.