French Drain Calculator

A 20 ft trench, 1 ft wide and 12 in deep, needs about 0.82 cubic yards of gravel and 22 ft of perforated pipe, including a 10% margin — enter your trench dimensions to get gravel, fabric, and pipe quantities.

Trench length (ft)

Trench width (ft)

Trench depth (in)

Waste margin (%)

Gravel

0.82 yd³

Fabric

88 ft²

Pipe

22 ft

Drainage gravel
0.82 yd³
per yd³ for Drainage gravel
Landscape fabric
88 ft²
per ft² for Landscape fabric
Perforated drain pipe
22 ft
per ft for Perforated drain pipe

Enter your local prices to see an estimated cost.

How we calculate this

Gravel volume = trench length × width × depth (in ÷ 12), plus your waste margin. Landscape fabric wraps the trench bottom and both side walls, so its area = length × (width + 2 × depth in feet). Pipe length matches the trench run plus waste, rounded up.

Estimates only. Check local codes and product labels. Read our full disclaimer.