French Drain Cost Calculator
Planning a French drain? Enter the trench dimensions to get the gravel needed (in cubic yards and tons), the length of perforated pipe to buy, and an estimated materials cost.
Common sizes
Jump to a pre-filled estimate:
How it works
Trench volume = length × width × depth. About 85% of that volume is gravel (the rest is pipe and fabric). We convert gravel to tons at ~1.4 tons per cubic yard, add ~5% extra pipe for connections, and total the materials at your local prices.
The formula
Gravel cu yd = (Length × Width in ÷ 12 × Depth in ÷ 12 × 0.85) ÷ 27. Tons ≈ yd³ × 1.4. Pipe ≈ length × 1.05. Cost = gravel tons × price + pipe ft × price.
Worked examples
| Example | Result |
|---|---|
| 50 ft × 12" × 18" | A typical yard drain run: about 2.4 cubic yards of gravel plus ~53 ft of pipe. |
| 100 ft perimeter drain | A foundation perimeter drain roughly doubles both gravel and pipe. |
Frequently asked questions
How much gravel for a French drain?
For a standard 12-inch-wide, 18-inch-deep trench, expect roughly 0.047 cubic yards of gravel per linear foot. A 50 ft run needs about 2.4 cubic yards (a little over 3 tons).
What size pipe for a French drain?
4-inch perforated corrugated or PVC pipe is standard for residential drains. Buy about 5% extra to allow for connections and trimming.
How deep should a French drain be?
Most French drains are 18–24 inches deep and 12 inches wide, sloped at least 1% (about 1 inch per 8 feet) so water flows to the outlet.
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Method reviewed by The editorial team. See our methodology for sources and assumptions.