Drainage trench material estimator

French Drain Calculator

Estimate gravel, perforated pipe, filter fabric, waste, and material cost for a French drain trench from length, width, and depth.

Units

Drain length (ft)Trench width (ft)Trench depth (ft)Pipe waste / fittings (%)Cost per gravel unit ($)Cost per pipe length ($)

Gravel to order

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Pipe length

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Filter fabric

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Estimated cost

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Drainage layout needs slope and outlet checks

This calculator estimates materials only. Confirm slope, discharge location, daylighting, cleanouts, utilities, stormwater rules, fabric overlap, and soil conditions before digging.

Android App

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French drain formula

Trench gravel yd³ = length × width × depth ÷ 27

Pipe length = trench length × (1 + waste %)

Fabric width = trench width + 2 × trench depth + overlap

Fabric area = fabric width × trench length

Example

A 60 ft drain trench that is 1 ft wide and 2 ft deep needs about 4.44 yd³ of gravel, 63 ft of pipe with 5% waste, and about 300 ft² of filter fabric.An 18 m drain trench that is 0.3 m wide and 0.6 m deep needs about 3.24 m³ of gravel, 19 m of pipe with 5% waste, and about 32 m² of filter fabric.

French Drain Calculator FAQ

How does this French drain calculator work?+

It multiplies measured job dimensions by the coverage, spacing, or package yield you enter, adds waste, then rounds the buy quantity up. Trench length, width, depth, and fabric overlap drive the estimate.It multiplies measured job dimensions by the coverage, spacing, or package yield you enter, adds waste, then rounds the buy quantity up. Trench length, width, depth, and fabric overlap drive the estimate.

Should I use the default waste value?+

Use the default for a quick planning estimate, then raise it for cuts, odd layouts, breakage, bad access, or product-specific loss.Use the default for a quick planning estimate, then raise it for cuts, odd layouts, breakage, bad access, or product-specific loss.

Is this a bid or code approval?+

No. It is a material planning calculator. Verify product data, local code, structural requirements, electrical requirements, and supplier packaging before ordering or building.No. It is a material planning calculator. Verify product data, local code, structural requirements, electrical requirements, and supplier packaging before ordering or building.