French Drain Calculator
Calculate gravel, pipe, and fabric needed for a French drain project.
Enter length, depth, and trench width.
French Drain Materials
French drain material calculations:
Trench Volume = Length × Depth × Width
Gravel Needed = Trench Volume (typically 80–90% of trench is gravel)
Pipe Length = Trench Length (plus fittings)
Landscape Fabric = 2 × (Depth + Width) × Length (lines the trench)
Unit conversions:
1 cubic yard = 27 cubic feet1 cubic meter = 35.31 cubic feet
Typical dimensions:
- Depth: 18–24 inches (45–60 cm)
- Width: 6–12 inches (15–30 cm)
- Pipe diameter: 4 inches (10 cm) perforated
- Gravel: ¾ inch washed stone
One cubic yard of gravel covers about 54 sq ft at 6 inches deep.