Drainage Gravel Calculator

Calculate gravel needed for a French drain or drainage trench, accounting for pipe displacement.

ft
in
in
in

Gravel Needed

2.6 cu yd

Poids approximatif3.7 tons
Total Trench Volume75.0 cu ft

Gravel Needed vs Trench Length

Voir la formule →

Formule

## Drainage Gravel Calculation **Gravel Volume = Trench Volume - Pipe Volume** The perforated pipe displaces some of the trench volume. Subtract its cross-sectional area multiplied by the trench length to get the net gravel volume. Use washed, angular gravel (3/4 to 1-1/2 inch) for good drainage.

Exemple Résolu

50 ft French drain, 12 in wide, 18 in deep, with 4-inch pipe.

  1. 01Trench volume = 50 x 1 x 1.5 = 75 cu ft
  2. 02Pipe volume = 50 x pi x (2/12) squared = 2.18 cu ft
  3. 03Gravel = (75 - 2.18) / 27 = 2.7 cu yd
  4. 04Weight = 2.7 x 1.4 = 3.8 tons