French Drain Gravel Calculator

How to calculate

Enter the gravel envelope rather than the full trench if topsoil covers the drain. Pipe volume is subtracted using its outside diameter. Fabric covers all four sides with one longitudinal overlap.

Worked example

Length (ft): 50 · Gravel envelope width (in): 12 · Gravel envelope depth (in): 18 · Pipe outside diameter (in): 4 · Fabric overlap (in): 12 · Extra material (%): 10.

These inputs produce 2.88 cubic yards of gravel. Change the measurements above to match your project.

Before you order

This does not size drainage capacity, grade, outlet or pipe perforations. Fabric end caps and fittings are extra. Confirm the design and underground utilities before excavation.

For an irregular footprint, split the project into rectangles. Calculate each section and combine unrounded quantities before rounding the final order. Ask the supplier to confirm product yield and available package sizes.

Common questions