Calculators · Plumber
Pipe Grade and Slope Calculator
Short answer
Pipe grade in percent is the drop divided by the run, times 100. A 1 % grade drops 10 mm per metre and a 2 % grade drops 20 mm per metre, so a 12 m run at 2 % drops 240 mm. Minimum grades for each pipe size are set by the plumbing code your province has adopted.
- Total drop
- 240 mm
- Drop per metre
- 20 mm/m
Formula
Drop (mm) = Length (m) × 1000 × Grade (%) ÷ 100
Worked example
A 12 m building drain at 2 %: 12 × 1000 × 2 ÷ 100 = 240 mm of fall, which is 20 mm per metre.
Before you rely on it
- Minimum and maximum grades by pipe size come from the National Plumbing Code and provincial codes. Check the edition that applies to you.
Studying for the Red Seal Plumber (306A) exam? Try 30 free practice questions or read the exam guide.