Construction

French Drain Calculator

Find gravel for a French drain trench.

Trench length

Trench width

Trench depth

Calculated Output

Gravel volume 0.037

Gravel weight 0.0525

Formula: yd³ = length × width × depth ÷ 27

Step-by-Step Breakdown

1. Values used:

2. Trench length = 1

3. Trench width = 1

4. Trench depth = 1

6. Gravel volume = 0.037

7. Gravel weight = 0.0525

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The math behind it

volume (ft³) = length × width × depth; ÷ 27 for cubic yards. Gravel ≈ 105 lb/ft³.

50 × 1 × 2 ft → 3.7 yd³.

Pipe space?

The perforated pipe displaces a little gravel — this gives a safe estimate.