French Drain Calculator
Compute drain gravel in cubic yards and tons for a trench, subtracting the perforated pipe's volume.
Processed locally in your browser — nothing is uploaded.
12 in is typical
18–24 in for most yard drains
4 in perforated pipe is standard
Enter the trench dimensions to estimate drain gravel.
About French Drain Calculator
Trench volume (length × width × depth) minus the cylinder of the perforated pipe gives the actual gravel needed. Results come in cubic yards with a waste factor and in tons at the editable 1.4 t/yd³ crushed-stone density.
Common uses
- Order drain rock for a yard drainage trench
- Estimate hauling weight for a curtain drain along a foundation
Example
Input
50 ft trench, 12 × 18 in, 4" pipe, 10% waste
Output
75 cu ft trench − 4.4 cu ft pipe → 2.88 yd³ ≈ 4.03 tons
Limitations
- Assumes gravel to the full trench depth; subtract if topping with soil and sod
- Fabric wrap and pipe fittings are not included