Roof Pitch Calculator
This roof pitch calculator will help you quickly assess the pitch of your roof and calculate the rafter length you need for your construction works. Convert pitch ratios, degrees, and percent slope — imperial and metric.
Pitch
Rafter Schedule & Lumber Cost
Birdsmouth Cut
Enter actual (not nominal) dimensions of your rafter lumber and wall plate.
Roofing Materials (Shingles)
- Angle
- 26.57°
- Slope
- 50.0%
- Rafter length
- 13.42 ft
- Rafter + overhang
- 14.42 ft
- Roof area multiplier
- ×1.1180
Rafter Schedule
- Rafter count
- 48
- Total linear footage
- 692.0 ft
- Ridge board
- 30.00 ft
- Fascia boards
- 108.00 ft
- Lumber cost est.
- $830.39
Birdsmouth Cut
- Seat cut depth
- 1.565 in
- Seat cut length
- 3.130 in
- Plumb cut height
- 5.685 in
Roofing Materials
- Roof area
- 885 sq ft
- Roofing squares
- 8.85
- Shingle bundles
- 27
- Underlayment rolls
- 3
- Ice & water shield
- 1 rolls
- Ridge cap bundles
- 1
- Material cost est.
- $1,062.58
Estimates for planning only. Verify on-site before cutting.
Common roof pitch chart
| Pitch (X:12) | Angle | Slope % |
|---|---|---|
| 2:12 | 9.5° | 16.7% |
| 3:12 | 14.0° | 25.0% |
| 4:12 | 18.4° | 33.3% |
| 5:12 | 22.6° | 41.7% |
| 6:12 | 26.6° | 50.0% |
| 7:12 | 30.3° | 58.3% |
| 8:12 | 33.7° | 66.7% |
| 9:12 | 36.9° | 75.0% |
| 12:12 | 45.0° | 100% |
How to determine roof pitch
This roof pitch calculator is a handy tool that helps you quickly assess the pitch of your roof and what length rafters you need for your construction works. You can also use it as a roof slope calculator to convert pitch from degrees to percent.
To estimate the total roofing material cost, you may want to use our Concrete Calculator or our Lumber Calculator for structural framing costs. We also have a full suite of Construction tools for your planning needs.
Step 1 — Measure rise & run
The rise is the vertical height of the roof. The run is the horizontal distance from the wall to directly below the ridge. Measure both in the same unit.
Step 2 — Calculate pitch ratio
Divide rise by run to get the pitch decimal. Multiply by 12 (imperial) or 10 (metric) for the pitch ratio — e.g. 0.5 × 12 = 6, so the pitch is 6:12.
Step 3 — Find rafter length
Use the Pythagorean theorem: rafter = √(rise² + run²). Add your eave overhang for the full cut length. Multiply by your roof area multiplier for total material.
Frequently asked questions
Accuracy & Review
Reviewed by: Liam Santos. Liam reviews our roofing and framing calculators to confirm accurate pitch conversions, rafter calculations, and practical construction defaults.
Last updated: May 2026
Important disclaimer: These estimates are for general planning purposes only. Actual rafter lengths depend on lumber species, crown direction, birdsmouth cut depth, and local building code requirements. Always verify measurements and consult a licensed contractor before cutting.
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