Quick answer

Pitch 6:12 -> 50% when run is 12 in the same units.

Formula

  • % = (rise / run) x 100
  • Pitch rise:12 = rise/12 x 100 when run is 12

Introduction

Contractors switch between pitch, percent, and degrees in the same meeting. The Slope Percentage Calculator keeps the triangle consistent.

Read slope percentage formula for the general case beyond pitch shorthand.

See roof numbers inside slope percentage examples for worked templates.

Pitch language vs percent

Pitch-in-12 is rise per foot of horizontal run when run is expressed as 12 in. It is a verbal shortcut, not a separate unit system.

Building standards discuss minimum slope for drainage. Percent and pitch both describe the same triangle if you write the actual rise and run.

Steep roofs push high percents quickly. A 9:12 pitch is 75% on the plan triangle.

Always field-verify with tape or laser because truss layout, hips, and valleys change local rise.

Formula and relationships

  • % = (rise/run) x 100
  • 6:12 -> 50%
  • 9:12 -> 75%

Angle comparisons: slope percentage vs degrees.

Rise-run primer: rise over run calculator.

Tool tips: slope percentage calculator guide.

Step-by-step guide

  1. Write pitch as rise and run. Example 4:12 means 4 ft rise per 12 ft run.
  2. Divide rise by run. 4/12 = 0.3333.
  3. Multiply by 100. 33.33% for 4:12 pitch.
  4. Check angle if needed. arctan(rise/run).

Common pitches

4:12 = 33.33%. 6:12 = 50%. 8:12 = 66.67%. 12:12 = 100% (45 degrees).

Low-slope commercial roofs may sit near 2:12 (about 16.67%) depending on membrane rules.