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French drain gravel calculator — tons + yards

Estimate washed stone for a French drain by trench volume minus the pipe displacement, then convert cubic yards to tons using a supplier density.

Adjust these to match your project.

ft
in
in
in
tons/yd³
%

10% is an ordering buffer for settling, compaction, and trench irregularity. The pipe volume is subtracted before that buffer is applied.

You'll need

4.0 tons

Drain stone

Drain stone volume
2.88 cubic yards

What this assumes

  • 50 ft × 12 in × 18 in trench minus 4 in pipe cylinder volume.
  • Stone volume includes +10% and converts at 1.4 tons/yd³.
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Coverage rates & sources

Every number this calculator uses is a published engineering constant — not an estimate we made up. Here is exactly what it assumes and where each value comes from.

  • Trench width (typical): 8–12 in (default 12)Source: Standard French-drain trench (drainage guidance)
  • Trench depth (typical): 18–24 in (default 18)Source: Standard French-drain depth
  • Recommended stone: #57 / 3/4 in washed angularSource: Standard French-drain stone (drainage guidance)
  • Pipe displacement: π/4 × D² × LSource: Geometry (cylinder volume of perforated pipe)
  • Gravel density: 1.4 tons/yd³Source: Typical washed-stone density (shared gravel table)
  • Cubic yard: 27 ft³Source: Standard unit conversion (1 yd = 3 ft -> 3³ = 27)

Before you buy

  • Uses #57 / 3/4 in washed stone and subtracts the pipe volume; many calculators skip that subtraction and over-order.
  • Tonnage depends on stone type and moisture; confirm the conversion with your supplier.
  • Wrap the gravel and pipe in filter fabric and design outlet/slope carefully; foundation or basement water should involve a pro.

This is a planning estimate, not a substitute for a pro's on-site measurement. For load-bearing, structural, or code-regulated work, confirm quantities with a licensed contractor.

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