Foundation Drainage Calculator
Estimate foundation-drain pipe rolls, drainage-stone volume, filter-fabric area and planning cost from perimeter length and editable trench dimensions.
Default project preview
2 pipe rolls
Drainage stone
6.52 yd³
Filter fabric
528 ft²
Fabric rolls
2
Purchased pipe length
200 ft
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.
Foundation drainage perimeter
Enter this project assumption in ft. The current imperial default is 160 ft.
Stone trench width
Enter this project assumption in in. The current imperial default is 12 in.
Stone depth
Enter this project assumption in in. The current imperial default is 12 in.
Stone allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 75.
Drain-pipe roll length
Enter this project assumption in ft. The current imperial default is 100 ft.
Fabric overlap allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Coverage per fabric roll
Enter this project assumption in ft². The current imperial default is 300 ft².
Price per pipe roll
Enter this project assumption in a unitless value. The current imperial default is 120. Minimum: 0.
Stone price
Enter this project assumption in per yd³. The current imperial default is 68 per yd³. Minimum: 0.
Price per fabric roll
Enter this project assumption in a unitless value. The current imperial default is 75. Minimum: 0.
How to read the outputs
Drainage stone
10% allowance included. Default preview: 6.52 yd³.
Filter fabric
trench base and sides estimate. Default preview: 528 ft².
Fabric rolls
300 ft² each. Default preview: 2.
Purchased pipe length
full rolls. Default preview: 200 ft.
Extra pipe capacity
above entered perimeter. Default preview: 40 ft.
Planning material cost
pipe, stone and fabric allowances. Default preview: $833.26.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Stone volume = perimeter × trench width × stone depth × allowance. Fabric area approximates perimeter × (trench width + two side depths) × overlap factor. Pipe and fabric rolls are rounded up.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: August 19, 2026
Estimate perimeter drain pipe rolls, drainage-stone volume and filter-fabric rolls from the actual foundation drainage perimeter and trench geometry.
Calculation steps
- 1Measure only foundation perimeter receiving the drainage system.
- 2Convert trench width and stone depth to volume along that perimeter.
- 3Apply the stone allowance after geometric volume is known.
- 4Calculate pipe rolls from perimeter length and fabric area from the trench wrap dimensions.
Worked numerical example
For 160 ft of foundation drain, a 12 in-wide by 12 in-deep stone envelope contains about 5.93 yd³ before allowance. A 10% stone allowance raises that to about 6.52 yd³, while 100 ft pipe rolls require two rolls for the perimeter.
Purchasing and rounding
Order washed drainage aggregate to supplier volume/weight conventions and confirm actual pipe-roll and fabric-roll sizes. Fittings, cleanouts, outlets and sump connections need separate counts.
Interpret the result
Stone, pipe and fabric are independent takeoffs. The stone result is not excavation volume, and fabric area depends on the assumed wrap geometry rather than foundation wall area.
Page-specific assumptions
- Drainage trench is reasonably uniform.
- One pipe run follows the entered perimeter.
- Fabric wraps the entered trench cross-section.
Common mistakes
- Using foundation floor area instead of perimeter.
- Counting soil excavation as drainage stone.
- Forgetting a positive outlet or sump path.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Foundation Drainage Calculator questions
Does this include waterproofing membrane?+
No. Waterproofing, protection board and drainage mat are separate materials.
Why wrap the stone with fabric?+
Filter fabric may help separate soil from drainage aggregate when specified for the assembly.
Is the entered perimeter always the pipe length?+
Add routing to outlets, cleanouts, sumps and connections when those lengths are not included in the perimeter.