What a 50 ft French drain takes
| Item | Amount |
|---|---|
| Drain rock (clean washed stone, 3/4 to 1½ in) | 2.88 cubic yards, 4.0 tons |
| Perforated pipe, 4 in | 50 ft (5 pieces of 10 ft) |
| Non-woven filter fabric | 250 sq ft |
| Soil to dig out | 2.8 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.
50 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 | 1.18 | 1.7 | 183 | 1.2 |
| 12 × 12 in | 1.86 | 2.6 | 200 | 1.9 |
| 12 × 18 in | 2.88 | 4.0 | 250 | 2.8 |
| 12 × 24 in | 3.90 | 5.5 | 300 | 3.7 |
| 18 × 24 in | 5.93 | 8.3 | 325 | 5.6 |
The arithmetic for 50 feet
A 50 ft drain in a 12 by 18 in trench is the calculator's own starting example, so the form above opens on these numbers. The trench is 50 × 1 × 1.5 = 75 cubic feet. The 4 in pipe takes up 4.4 cubic feet, leaving 70.6. Add 10% for uneven trench walls: 77.7 cubic feet.
Divide by 27 for cubic yards, 2.88, and multiply by 1.4 for tons of washed stone, 4.03. Round up to the next amount your supplier sells.
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 50 foot French drain?
About 2.9 cubic yards, or 4.0 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 3.9 cubic yards.
How many tons of gravel for a 50 ft French drain?
About 4.0 tons (2.9 cubic yards) for a trench 12 in wide and 18 in deep with a 4 in pipe and 10% extra.
How much gravel for a 50 ft French drain 12 inches deep?
About 1.9 cubic yards (2.6 tons) for a trench 12 in wide.
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.