Selected rock
River Rock
Rounded decorative stone for beds, drainage swales, and dry creek looks.
Smooth rounded stones, often mixed colors. Planning density: 105 lb/ft3.French drain gravel by trench length
| Trench (Length x Width) | Depth 6" | Depth 12" | Depth 18" |
|---|---|---|---|
| 25 ft x 1 ft | 0.46 yd3 | 0.93 yd3 | 1.39 yd3 |
| 50 ft x 1 ft | 0.93 yd3 | 1.85 yd3 | 2.78 yd3 |
| 100 ft x 1 ft | 1.85 yd3 | 3.70 yd3 | 5.56 yd3 |
| 50 ft x 1.5 ft | 1.39 yd3 | 2.78 yd3 | 4.17 yd3 |
Frequently Asked Questions
How much gravel do I need for a French drain?
French drains commonly need 6-12 in of gravel around the pipe. For a 50 ft trench that is 12 in wide and 12 in filled with rock, the trench volume is about 1.85 cubic yards before subtracting pipe displacement or adding waste.
What type of gravel is best for French drains?
#57 crushed stone or clean drain rock is commonly used because open voids let water move. Rounded river rock can work when sized correctly. Avoid products with fines that can clog drainage.
How deep should a French drain be?
Many residential French drains are roughly 18-24 inches deep overall, but the needed depth depends on outlet elevation, slope, soil, and the water problem. This page estimates the gravel portion only.
Do I need landscape fabric with French drain gravel?
Landscape fabric is commonly used to separate soil from the drain rock and reduce migration of fines into the trench. Follow product and local drainage guidance for the site.
How do I calculate gravel for a French drain trench?
Trench length x width x gravel fill height, all in feet, divided by 27 = cubic yards. The newer drain rock calculator can also subtract the round pipe volume from the trench volume.