French Drain Calculator

Summary

Estimate the volume of gravel and length of perforated pipe needed for a French drain system.

How it works

1. Enter the total length of your French drain trench.
2. Enter the trench width and depth (typical: 12–24 in wide, 18–36 in deep).
3. Choose a pipe diameter to calculate the pipe void volume deducted from gravel.
4. Add a waste factor (5–10% recommended) to account for settling and spillage.
5. Click Calculate to see gravel volume and pipe length results.
6. Use the results to order materials from your local supplier.

Use cases

• Planning a yard drainage French drain to redirect surface water.
• Installing a foundation perimeter drain to protect a basement.
• Designing a curtain drain on a hillside to intercept groundwater.
• Estimating materials for a driveway edge drainage channel.
• Budgeting gravel and pipe for a retaining wall drainage system.
• Calculating materials for an agricultural field drainage project.

Frequently Asked Questions