French Drain Calculator
Enter your trench length, width, and depth — get the gravel in cubic yards and tons, plus the pipe and filter fabric you need.
Gravel includes ~5% extra and accounts for the pipe. Use clean #57 / drain rock (~1.4 tons per cubic yard), wrap the trench in filter fabric, and slope at least 1% so water actually runs to the outlet.
How the French drain calculator works
Gravel cubic yards = (length × width × depth in feet) ÷ 27, minus the pipe's volume. Multiply yards by ~1.4 for tons, since drain rock is sold by weight as often as by yard. Filter fabric wraps the trench, so you need a strip wide enough to line the bottom, both walls, and overlap on top.
Slope is what makes it work
A French drain with no fall is just a buried puddle. Aim for at least 1% slope — about 1 inch of drop every 8–10 feet — toward a daylight outlet or dry well. Holes in the pipe face down so water enters low.
Tired of a soggy yard?
We install French drains, channel drains, and regrade yards across North Port, Venice, Port Charlotte & Englewood — sloped right so the water actually leaves.
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