Pitch Converter – Degrees, Ratio & Percent

This tool applies the formula % = tan(θ) × 100; Ratio = tan(θ) × 12 directly to the measurements you enter, so the result is an exact quantity rather than a rough guess. Because pitch conversion is priced and delivered per unit - cubic meters, square meters, bags or tonnes - a small measurement error multiplies across the entire order, which is why the calculation is worth doing properly. Worked example: Input 40% slope: angle = arctan(0.4) = 21.8°, ratio 4.8:12, rafter multiplier 1.077. One note from practice: Percent slope is what site levels read - convert once, order right once. Enter the one of: degrees, ratio or percent, check the totals, then round up to the nearest whole bag, sheet or roll before you place the order.

1. 1

   Measure the space

   Record the one of: degrees, ratio or percent at the widest and longest points.

2. 2

   Enter the values

   Type the measurements into the calculator and select your units.

3. 3

   Apply the formula

   The tool computes % = tan(θ) × 100; Ratio = tan(θ) × 12 for your inputs instantly.

4. 4

   Add waste and order

   Review the total with a 5-10% margin and round up to whole units.

• Using footprint as roof area

• Ordering zero waste

• Shallow pitch with shingles