What a 25 ft French drain takes
| Item | Amount |
|---|---|
| Drain rock (clean washed stone, 3/4 to 1½ in) | 1.44 cubic yards, 2.0 tons |
| Perforated pipe, 4 in | 25 ft (3 pieces of 10 ft) |
| Non-woven filter fabric | 125 sq ft |
| Soil to dig out | 1.4 cubic yards |
For a trench 12 in wide and 18 in deep, with 10% extra stone for uneven trench walls and settling. The stone is the trench volume less the space the pipe takes up, at 1.4 tons per cubic yard.
25 ft of drain, by trench size
Width × depth of the trench, with a 4 in pipe and 10% extra stone.
| Trench | Drain rock, cubic yards | Tons | Fabric, sq ft | Soil dug out, cubic yards |
|---|---|---|---|---|
| 8 × 12 in | 0.59 | 0.8 | 92 | 0.6 |
| 12 × 12 in | 0.93 | 1.3 | 100 | 0.9 |
| 12 × 18 in | 1.44 | 2.0 | 125 | 1.4 |
| 12 × 24 in | 1.95 | 2.7 | 150 | 1.9 |
| 18 × 24 in | 2.97 | 4.2 | 163 | 2.8 |
Pipe and fabric for 25 feet
Perforated pipe is sold in 10 ft sticks and in longer coils. For 25 ft you need 3 pieces of 10 ft, with the last one cut, or one coil of at least 25 ft. A coil has no joints to fit in the trench.
The fabric has to wrap the stone on all sides and overlap on top, so for a 12 by 18 in trench it needs to be 60 inches (5 ft) wide: 125 sq ft for the 25 ft run. Buy a roll at least that wide, so there is no seam along the trench for soil to wash through.
Use clean, washed stone with no fines, wrap the stone (not the pipe) in the fabric, and make sure the drain has an outlet. The fittings, tools and steps are in the French drain materials list, and the method behind the stone figure is in how much gravel for a French drain.
Want to change anything else? The calculator above is the full French Drain Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How much gravel do I need for a 25 foot French drain?
About 1.4 cubic yards, or 2.0 tons, of clean drain rock for a trench 12 in wide and 18 in deep with a 4 in pipe, including 10% extra. A 12 by 24 in trench takes 1.9 cubic yards.
How wide should the fabric be for a French drain?
For a trench 12 in wide and 18 in deep, 60 inches: the width, twice the depth and 12 inches of overlap. A 25 ft run takes 125 sq ft.
How many yards of gravel for a 25 ft French drain?
About 1.4 cubic yards (2.0 tons) for a 12 by 18 in trench with a 4 in pipe and 10% extra.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.