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French Drain Calculator

Estimate gravel volume and pipe length for a basic French drain project.

Updated April 16, 2026
Free online tool
Planning and research use

Why this page exists

Drainage work is easier to plan when trench dimensions turn into a practical materials estimate instead of being guessed in the yard. This calculator helps visitors estimate French drain trench volume, gravel volume, and pipe length for a simple residential planning pass.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

French drain calculator

Estimate trench volume, gravel volume, and pipe length for a basic French drain project.

Result

3.33 cubic yards

Estimated trench volume and gravel needed for a basic French drain, along with the pipe length used in the estimate.

Gravel volume needed3.33 cu yd

Trench volume90.0 cu ft

Estimated pipe length used60.0 ft

Trench dimensions used60.0 ft × 1.0 ft × 1.5 ft

60.0 feet of trench at 1.0 feet wide and 1.5 feet deep works out to about 90.0 cubic feet of trench volume.
The pipe-length planning number is 60.0 feet in this estimate.
Use the result as a basic materials estimate only, because drainage fabric, pipe diameter, slope, and outlet details can still change the full project plan.

This is a planning estimate. Real French-drain projects may also need fabric, slope planning, outlet design, and local drainage review.

Planning note

Last updated April 16, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter trench length, trench width, trench depth, and the pipe length you want to use in the estimate.

The calculator multiplies the trench dimensions to estimate trench and gravel volume.

It also shows the pipe length used so the trench and pipe plan stay aligned in one place.

Understanding your result

This is a basic materials estimate, not a drainage design. Real projects may also need fabric, slope planning, outlet routing, and local drainage review.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Estimate gravel for a straight backyard drain run

A volume number can make it easier to compare delivery options or bag counts before digging starts.

Compare trench-size options

Changing width or depth can quickly show how much more gravel a larger trench will require.

Use it with slope and gravel tools

French drain planning often fits naturally beside pipe-slope and gravel estimates.

FAQ

Common questions

How is gravel volume estimated here?

The calculator multiplies trench length, width, and depth to estimate trench volume and uses that as a simple gravel-planning number.

Why include pipe length separately?

Because some projects use a pipe run that differs from the trench length, especially when connections or outlet routing change the layout.

Why is this not a full drainage design?

Because real French drain performance depends on slope, fabric, outlet conditions, soil behavior, and local drainage considerations beyond a simple materials estimate.

Related tools

Keep comparing

Use these related tools to compare nearby scenarios, check a second estimate, or keep narrowing down the right decision.

Home ToolsUpdated April 14, 2026