French Drain Calculator
Estimate gravel and pipe for a French drain.
Use the French drain calculator to estimate the gravel volume, pipe length, and filter fabric needed for a French drain. Gravel is calculated from the trench dimensions and converted to cubic yards. Pipe length includes 10% extra, while the fabric estimate covers the bottom and sides of the trench.
Gravel
3.7
5.19 tons
Perforated pipe
56
ft (+10%)
Filter fabric
250
ft²
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Recommended tools & materials
Handy picks for this project on Amazon.
Landscape Fabric
Stops weeds under gravel and mulch
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Steel Garden Rake
Spread gravel, soil and mulch evenly
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Heavy-Duty Wheelbarrow
Move bulk material fast
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Hand Tamper
Compact base layers before paving
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How does the french drain calculator work?
Gravel volume = trench length × width × depth (all in ft), converted to cubic yards. Pipe length equals trench length + 10%. Fabric wraps the trench bottom and sides.
What else do people ask about this calculator?
How deep should a French drain be?
Typical residential drains are 18–24 in deep, with the perforated pipe pitched 1% (1 in per 8 ft).
Do I need filter fabric?
Yes — wrapping the trench in geotextile keeps soil out of the gravel and stops the drain from silting up.
Which related calculators should I use next?
Where can I learn more about these materials?
Weights, coverage, types and buying tips for the materials this calculator estimates.
Gravel guide
How much gravel you need, what a cubic yard weighs, and which type fits your project.
Crushed Stone guide
Crushed stone sizes suit different applications: #57 stone is commonly used for drainage, concrete, and paver bases; #8 stone works for fine paver bedding, chip seal, and decorative applications; and ¾″ minus, also called crusher run, compacts into a hard driveway base.
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Tools to Complete Your French Drain
These practical tools help you excavate the trench, move gravel and compact the finished drain bed.
AMES Steel Garden Rake
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Gorilla Carts Dump Cart
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VEVOR Hand Tamper
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