Convert roof slope between rise and run, X:12 pitch, degrees, percentage, ratio, and slope factor. Optionally estimate rise and simple sloped length from a horizontal run or centered gable span.
Generated from the same conversion engine used above.
| Pitch | Angle | Slope | Factor |
|---|---|---|---|
| 1:12 | 4.76° | 8.33% | 1.003466 |
| 2:12 | 9.46° | 16.67% | 1.013794 |
| 3:12 | 14.04° | 25% | 1.030776 |
| 4:12 | 18.43° | 33.33% | 1.054093 |
| 5:12 | 22.62° | 41.67% | 1.083333 |
| 6:12 | 26.57° | 50% | 1.118034 |
| 7:12 | 30.26° | 58.33% | 1.157704 |
| 8:12 | 33.69° | 66.67% | 1.20185 |
| 9:12 | 36.87° | 75% | 1.25 |
| 10:12 | 39.81° | 83.33% | 1.301708 |
| 12:12 | 45° | 100% | 1.414214 |
Roof pitch describes vertical rise relative to horizontal run. A 6:12 pitch rises 6 units for every 12 horizontal units; it does not mean 6 degrees.
Every supported input is normalized to one decimal slope, rise divided by run. Angle, percentage, pitch-per-12, ratio, and slope factor are then derived consistently.
rise ÷ horizontal rundecimal slope × 12arctangent(decimal slope)decimal slope × 100√(1 + decimal slope²)horizontal run × decimal slopehorizontal run × slope factorA 6:12 pitch has a 0.5 decimal slope, 26.565° angle, 50% slope, 1:2 ratio, and 1.118034 slope factor.
A 4:12 pitch has a 0.333333 slope, approximately 18.435°, 33.333%, and a 1.054093 slope factor.
A 30° angle converts to approximately 6.93:12 and 57.74%.
A 25% slope is 0.25, or 3:12, with an angle of approximately 14.036°.
At 6:12, a 10-ft horizontal run rises 5 ft and has a simple sloped length of about 11.18 ft.
Run is the horizontal projection, not the sloped roof surface.
A 100% slope equals 45°, not 100°.
The optional span calculation assumes run is exactly half the total span.
Use the Rafter Calculator for overhang and ridge adjustments, and Roofing Calculator for roof-area materials and waste.
X:12 notation reports units of rise per 12 units of horizontal run. The calculator supports 0:12 and pitches steeper than 12:12.
Degrees come from the arctangent of decimal slope. For example, 6:12 is about 26.57°, not 6°.
Angle mode converts degrees below 90° into slope, then expresses that slope per 12 units of run.
Slope percentage is rise divided by horizontal run times 100. It is a different measurement from angular degrees.
Slope factor converts a simple horizontal projected length or area to its sloped equivalent. A 6:12 factor of about 1.118 turns 100 square feet of simple projection into about 111.8 square feet before complexity or waste.
Run mode calculates vertical rise and simple sloped length. Span mode first divides a centered symmetrical gable span by two. Neither includes overhang, ridge adjustment, birdsmouths, or cuts.
This geometry calculator does not determine product suitability, drainage, minimum code pitch, structural requirements, rafter sizing, or snow and wind loads.
Roof pitch is vertical rise relative to horizontal run, commonly written as rise per 12 units of run.
Divide rise by horizontal run. Multiply by 12 for X:12 notation, or by 100 for percentage.
Approximately 18.43 degrees.
Approximately 26.57 degrees.
Approximately 33.69 degrees.
The roof rises 6 units for every 12 horizontal units.
Divide rise by run and take the arctangent of that decimal slope.
Take the tangent of the angle to get decimal slope, then multiply by 12.
No. A 100% slope has equal rise and run and therefore equals 45 degrees.
It is the multiplier that converts horizontal projected length or simple planar area to sloped length or area.
Multiply horizontal run by decimal slope.
No. Rafter length can also involve overhang, ridge adjustment, seat cuts, and structural details.
No. Product suitability, drainage, structural design, and code requirements must be verified separately.