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Gravel, pipe, and fabric quantities for a French drain trench of any length and depth.
With these inputs:
| Result | Value |
|---|---|
| Washed stone needed | 2.37 yd³ |
| Weight | 3.32 tons |
| Perforated pipe | 50 linear ft |
| Geotextile fabric | 225 sq ft |
| Trench | 50 ft × 12" wide × 18" deep |
| Total trench volume | 2.78 yd³ |
| Topsoil cap | 3 in |
| Volume displaced by pipe | 0.16 yd³ |
| Stone volume | 2.37 yd³ |
| Stone weight | 3.32 tons |
| Recommended stone | #57 Crushed Stone (3/4") — washed, no fines |
| Fabric roll width needed | 4.5 ft |
| Estimated stone cost | $99 – $182 |
Use washed stone with no fines — #57 is the standard. Stone with dust in it will silt up and clog the drain. Wrap the trench in geotextile fabric and slope it at least 1% (1 inch of fall per 8 feet).
A French drain is a trench, a perforated pipe, and a lot of washed stone. This calculator sizes the stone around the pipe correctly — subtracting the volume the pipe itself occupies — and returns the fabric and pipe lengths you need to buy alongside it.
Washed #57 crushed stone, roughly 3/4 inch, with no fines. The washing matters — any stone dust will migrate into the voids and clog the drain over time.
A standard 12-inch wide, 18-inch deep trench uses about 0.045 cubic yards per linear foot after subtracting the pipe. A 50-foot drain needs roughly 2.3 cubic yards, or about 3.2 tons.
Typically 18 to 24 inches deep and 12 inches wide. It must slope continuously toward the outlet at a minimum of 1%, which is 1 inch of drop for every 8 feet of run.
Yes. Geotextile fabric wrapped around the stone keeps soil fines out of the drainage voids. Without it, a French drain silts up and stops working within a few years.
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