French Drain Fabric Calculator
Estimate geotextile fabric for a French drain from trench dimensions, length, top overlap, end laps, waste and roll size.
Default project preview
2 rolls
Required wrap width
8 ft
Fabric area
1,056 ft²
Length segments
1
Purchased fabric area
7,500 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Drain trench length
Enter this project assumption in ft. The current imperial default is 120 ft.
Trench width
Enter this project assumption in ft. The current imperial default is 2 ft.
Fabric-lined depth
Enter this project assumption in ft. The current imperial default is 2.5 ft.
Top closure overlap
Enter this project assumption in in. The current imperial default is 12 in. Minimum: 0.
End overlap between fabric lengths
Enter this project assumption in in. The current imperial default is 18 in. Minimum: 0.
Cuts and damage allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Fabric roll width
Enter this project assumption in ft. The current imperial default is 12.5 ft.
Fabric roll length
Enter this project assumption in ft. The current imperial default is 300 ft.
Price per roll
Enter this project assumption in a unitless value. The current imperial default is 245. Minimum: 0.
How to read the outputs
Required wrap width
bottom + both sides + top overlap. Default preview: 8 ft.
Fabric area
includes waste. Default preview: 1,056 ft².
Length segments
before waste allowance. Default preview: 1.
Purchased fabric area
full rolls. Default preview: 7,500 ft².
End overlap
between length segments. Default preview: 1.5 ft.
Fabric cost
full rolls. Default preview: $490.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Wrap width = trench bottom width + two lined depths + top overlap. Determine strips across the roll and length segments with end overlap, then add waste and round to full rolls.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
French Drain Fabric Calculator questions
Should fabric completely wrap the stone?+
Many French-drain details line the trench and fold fabric over the aggregate, but the project detail controls the arrangement.
Is landscape fabric the same as drainage geotextile?+
Not always. Select a geotextile intended for filtration and drainage with properties suitable for the soil.
Why can a wide roll reduce waste?+
A wide roll may yield multiple full trench-wrap strips, reducing seams and offcuts.