HomeFrench drain calculator
French drain calculator
A 100-foot French drain in a 12 by 24 inch trench takes about 7.1 cubic yards of washed stone (9.9 tons at 1.4 tons a yard), 100 feet of 4-inch perforated pipe and 600 square feet of filter fabric. Guides price it at $1,000 to $10,000, or $10 to $100 a foot, installed. Change the numbers below and the quantities and the price update.
A drain only matters where water sits near the footing. USDA's soil survey rates a shallow water table a limit for basements on more than half the mapped land in 1,061 of the 3,122 US counties it covers, so the calculator also looks up your ZIP code's county (USDA SSURGO, August 5, 2026).
Exterior or yard drain · 100 ft · 12 x 24 in trench
washed stone (9.9 tons at 1.4 tons a yard)
4-inch perforated pipe, plus the run to daylight or the sump
filter fabric to wrap the stone, with a top overlap
published price for the run ($10 to $100 a foot)
The price is the median low and high end of 5 sources for this drain type times 100 feet. Guides price a drain by the foot with digging, pipe, stone and fabric included, so stone is counted separately here only so you can check a quote's materials line.
The published average is $45 a foot, $4,500 for this run. The published ranges are wide, and the metro figures further down the page are narrower.
| Source | Where | Published range | Average | Page updated |
|---|---|---|---|---|
| HomeAdvisor | US | $10 to $100 per linear ft | $45 | June 20, 2026 |
| This Old House | US | $10 to $100 per linear ft | March 4, 2026 | |
| HomeGuide | US | $10 to $35 per linear ft (exterior yard or curtain drain) | February 5, 2026 | |
| Forbes Home | US | $10 to $100 per linear ft (exterior) | February 7, 2025 | |
| Fixr | US | $10 to $100 per linear ft (exterior) | January 31, 2025 |
Is the water table high where you live?
This is the county's share of land where USDA records a saturated zone within about 6 feet of the surface for part of the year. It is a county figure, not the water level at one lot. For a depth at one address, use USDA's Web Soil Survey or nearby well records.
Example result
ZIP 43215 · Franklin County, OH
of Franklin County's mapped land: a shallow water table limits basements
inside Columbus city limits
USDA's soil survey records a saturated zone within about 6 feet of the surface for part of the year on more than half of the county's mapped land. That is a county share, not the water level at one lot, and it doesn't say whether a drain is needed. Surface fixes (gutters, downspouts, grade) come first, and a drain on a lot with a high water table usually needs a place to send the water, such as a sump pit or daylight. Full Franklin County page.
How the calculator works
Stone is the trench's volume minus the pipe's: width x depth x length in cubic feet, minus the 4-inch pipe's own volume, divided by 27. Fabric wraps the stone on the bottom and both walls with a top overlap as wide as the trench, so its width is twice the depth plus twice the width. Pipe equals the run length; add the stretch to daylight or the sump.
Tons depend on the stone. Published conversions for crushed stone run from 1.2 to 1.5 tons per cubic yard: TheSiteMath gives 1.4 to 1.5 for crushed gravel, Remodel Calculators 1.2 to 1.4 and Invoice Mama 1.5 (read October 3, 2026). The box above uses 1.4; your supplier's ticket decides.
The price is the median low and high end of the per-foot ranges 7 cost guides publish for the drain type you pick, times the length, read on September 28, 2026. A guide's range already includes digging, pipe, stone and fabric. It is a published range, not a quote.
Worked example: 100 ft x (12 in / 12) x (24 in / 12) = 200 cubic feet of trench; the 4-inch pipe takes about 8.7 cubic feet of that, which leaves 191.3 cubic feet, or 7.1 cubic yards. At 1.4 tons a yard that is 9.9 tons.
Before you dig
University of Minnesota Extension says a great number of basement water problems can be solved with gutters, downspouts with extenders and a grade that slopes away from the house, and that this should come before any below-grade drainage system (UMN Extension). A foundation drain empties to daylight or to a sump pit that a pump empties (DOE Building America), and the 2024 International Residential Code requires one around concrete or masonry foundations that hold back earth and enclose space below grade, with exceptions (IRC R405.1). More in the foundation drain guide, which lists the 1,061 high water table counties and every published price.
Per-foot prices in four metros
Angi publishes a French drain price per foot for these cities, pages updated June 17, 2026 to June 19, 2026:
- Houston, TX: $20 to $50 a foot (Angi)
- Dallas, TX: $25 to $55 a foot (Angi)
- Austin, TX: $20 to $50 a foot (Angi)
- Columbus, OH: $20 to $50 a foot (Angi)
Related calculators and costs: foundation repair cost calculator, basement waterproofing costs, wet basements and soil and water table by ZIP code.
Sources: cost guides linked in the tables (read September 28, 2026) · USDA SSURGO (August 5, 2026) · IRC 2024 R405.1 · UMN Extension · DOE Building America. Methods