💧 Free Calculator
French Drain Calculator
Estimate gravel, pipe, and fabric needed for drainage systems. Calculate trench volume, gravel tons, and pipe length.
💧 French Drain Materials
0 tons gravel
💧 French drain formula: Gravel volume = (Length × Width × Gravel Depth) ÷ 27 for cubic yards. Gravel weight: ~1.4 tons per cubic yard. Pipe length = trench length.
💡 Pro tip: Use 3/4″ washed gravel for best drainage. Wrap pipe with filter fabric or use sock pipe to prevent clogging. Slope drain 1-2% (1-2 ft per 100 ft) for proper water flow.