Drain Slope Calculator

Calculate the total vertical drop and grade for a gravity drain line.

rundrop1/4 in/ft
TOTAL DROP
in
over the run

Usage Tip

Too little slope and solids settle; too much and water outruns solids. 1/4 in per foot is the sweet spot.

THE MATH
drop = L × slope
Where: L = run length  •  grade % = (slope ÷ 12) × 100
• 1/4 in per foot is the standard for most drains
• Confirm against local code
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