Roofing reference guide
Roof pitch chart for degrees, percent, and slope factor
Convert rise per 12 into the angle, percentage slope, area factor, and sloped length used in roof measurements and material estimates.
Calculate roof area01 / Read the ratio
What a roof pitch such as 6:12 means
A 6:12 roof rises 6 units for every 12 units of horizontal run. The two measurements must use the same unit. You can use inches, centimetres, feet, or metres because pitch is a ratio.
This guide uses the common rise-per-12 meaning that people usually expect from a roof pitch chart. Some technical references distinguish slope as rise divided by horizontal run and pitch as rise divided by the full span. The GAF Steep-Slope Pro Field Guide shows that terminology distinction. Check the notation used on the project documents instead of assuming the denominator.
02 / Use the chart
Roof pitch conversion chart
Use the row that matches the rise for every 12 units of horizontal run. Values are rounded for display. The formulas in the next section produce the unrounded result for any pitch, including a pitch between listed rows.
| Pitch | Angle | Slope | Factor | Sloped length per 12 |
|---|---|---|---|---|
| 0:12 | 0.00° | 0.00% | 1.0000 | 12.000 |
| 0.25:12 | 1.19° | 2.08% | 1.0002 | 12.003 |
| 0.5:12 | 2.39° | 4.17% | 1.0009 | 12.010 |
| 1:12 | 4.76° | 8.33% | 1.0035 | 12.042 |
| 2:12 | 9.46° | 16.67% | 1.0138 | 12.166 |
| 3:12 | 14.04° | 25.00% | 1.0308 | 12.369 |
| 4:12 | 18.43° | 33.33% | 1.0541 | 12.649 |
| 5:12 | 22.62° | 41.67% | 1.0833 | 13.000 |
| 6:12 | 26.57° | 50.00% | 1.1180 | 13.416 |
| 7:12 | 30.26° | 58.33% | 1.1577 | 13.892 |
| 8:12 | 33.69° | 66.67% | 1.2019 | 14.422 |
| 9:12 | 36.87° | 75.00% | 1.2500 | 15.000 |
| 10:12 | 39.81° | 83.33% | 1.3017 | 15.620 |
| 11:12 | 42.51° | 91.67% | 1.3566 | 16.279 |
| 12:12 | 45.00° | 100.00% | 1.4142 | 16.971 |
| 14:12 | 49.40° | 116.67% | 1.5366 | 18.439 |
| 16:12 | 53.13° | 133.33% | 1.6667 | 20.000 |
| 18:12 | 56.31° | 150.00% | 1.8028 | 21.633 |
| 20:12 | 59.04° | 166.67% | 1.9437 | 23.324 |
| 24:12 | 63.43° | 200.00% | 2.2361 | 26.833 |
The ASC Building Products pitch and roof-angle job aid provides an industry example of pitch-to-degree conversion. Its flashing angles and product details are not inputs or recommendations in this chart.
03 / Check the calculation
Roof pitch formulas
Let R be the vertical rise over a horizontal run of 12. These equations come from the same right triangle shown above.
θ = arctan(R ÷ 12)(R ÷ 12) × 100√(1 + (R ÷ 12)²)√(R² + 12²)Worked example: 6:12 pitch
- Ratio: 6 ÷ 12 = 0.5
- Angle: arctan(0.5) = 26.565°, which displays as 26.57°
- Percentage slope: 0.5 × 100 = 50%
- Slope factor: √(1 + 0.5²) = √1.25 = 1.118034
- Sloped length per 12: 12 × 1.118034 = 13.416 units
04 / Apply the factor
Use the slope factor for roof area, not as waste
The slope factor converts a horizontal projected area into the surface area of one plane with a constant pitch. For example, 1,200 ft² of horizontal plan area at 6:12 becomes 1,200 × 1.118034, or approximately 1,341.641 ft² of sloped area.
That result is geometry only. It does not include a material allowance, package rounding, laps, cuts, openings, ridges, valleys, flashing, or accessories. Use the Roof Area Calculator to combine measured sections and keep its optional user-selected allowance separate from the geometric area.
05 / Continue the estimate
Choose the next roofing calculation
Find the sloped surface
Use the Roof Area Calculator for multiple sections, mixed pitches, and roofing squares.
Find length or layout
Use the Metal Roof Panel Length Calculator for one strip, or the layout planner for rows, columns, laps, and cuts.
Convert area into units
Continue with the shingle, sheathing, or underlayment calculator after the sloped area is verified.
06 / Keep the boundary clear
What this roof pitch chart does not decide
- It does not size rafters, trusses, beams, fasteners, connections, or structural members.
- It does not calculate hip, valley, jack-rafter, compound, birdsmouth, or saw-cut geometry.
- It does not select a roof covering or establish a permissible minimum or maximum slope.
- It does not determine drainage, snow behavior, wind resistance, fall protection, or code compliance.
- It assumes one straight, constant slope. Measure and calculate different roof planes separately.
A chart does not make roof access safe. In the United States, review OSHA residential fall-protection guidance and the requirements that apply to the work. Prefer verified drawings or safely accessible measurements. Qualified people should plan any work at height.
Common questions
Roof pitch chart FAQ
What angle is a 4:12 roof pitch?
A 4:12 pitch is approximately 18.43°. It is also a 33.33% slope with a slope factor of about 1.0541.
What angle is a 6:12 roof pitch?
A 6:12 pitch is approximately 26.57°. It is also a 50% slope with a slope factor of about 1.1180.
Is a 100% slope the same as 100 degrees?
No. A 100% slope means rise equals horizontal run. That is a 12:12 pitch and a 45° angle.
Does roof pitch change in Metric units?
No. A ratio is unitless when rise and run use the same unit. A rise of 15 cm over a 30 cm horizontal run has the same slope as 6 inches over 12 inches.
Is the slope factor a waste percentage?
No. It accounts only for the extra surface area created by the slope. Material allowance, laps, cuts, damage, and package rounding are separate decisions.
Can this chart tell me which roofing material to use?
No. Material suitability depends on the exact product, assembly, manufacturer instructions, project documents, and applicable local requirements.
Next step
Know the pitch and horizontal roof dimensions?
Calculate the true sloped surface area before estimating packages or adding an ordering allowance.