French Drain Cost Calculator
A French drain cost calculator multiplies trench length by a material rate and a labor rate per foot, so a 50 ft drain at $6 and $8 per foot costs $700.
French drain cost calculator formula
A French drain cost calculator finds the price by multiplying the length of the trench by two rates, one for materials and one for labor, both per linear foot. Total cost = length × material rate + length × labor rate. The starting rates in the tool are $6 and $8 per foot. They are placeholders, so type in numbers from a local quote.
The formula in plain words
Take the number of feet you plan to dig. Multiply it by what the pipe, stone and fabric cost per foot. Multiply it again by what the crew or rental charges per foot. Add the two results.
The calculator does not guess at soil type, depth or access. If your quote is a lump sum, divide it by the footage to see what rate the contractor is really using.
Worked examples
These match the calculator exactly.
- Backyard drain along a low spot: 50 ft at $6 per ft material and $8 per ft labor
- Material: 50 × $6 = $300
- Labor: 50 × $8 = $400
- Total: $700
- Longer run around a house corner: 120 ft at $7 per ft material and $10 per ft labor
- Material: 120 × $7 = $840
- Labor: 120 × $10 = $1,200
- Total: $2,040
In both cases labor is more than half the bill. That is typical, and it is why a short trench through open grass costs so much less per foot than a long one threading past a patio.
What goes into each rate
| Part of the job | Counts as | What changes the price |
|---|---|---|
| Perforated pipe | Material | Diameter and wall type |
| Washed stone | Material | Local quarry price and trench width |
| Filter fabric | Material | Wrap width, one roll covers many feet |
| Solid outlet pipe | Material | Distance to where the water exits |
| Digging the trench | Labor | Roots, rock, clay, hand or machine |
| Setting slope and laying pipe | Labor | How level the ground already is |
| Hauling away soil | Labor | Dump distance and how much stone replaces it |
| Restoring sod or paving | Labor | Often quoted as a separate item |
How to measure the length
Walk the route you want the water to take and measure it with a tape or a measuring wheel. Start at the wet spot and finish at the place the water will leave. Follow every bend, since a curved route is longer than the straight line between the ends.
Add the outlet pipe if it runs through a separate trench. Mark the route with paint before you measure so that the number matches what the crew will dig.
What a deeper or wider trench does to the price
The calculator uses a single rate per foot, so a deeper trench is not built in. You have to raise the rate yourself. A trench that is 18 inches deep and 6 inches wide moves much less soil than one that is 30 inches deep and 12 inches wide. The deeper one also needs more stone per foot. If a contractor quotes a higher per foot rate for a deeper drain, use that rate in the labor box and let the tool do the multiplication.
Getting quotes to compare
Ask two or three local contractors for a price on the same route. Tell each one the length, where the water should exit, and whether anything blocks the path, like a walkway or a tree. Divide each total by the footage. If one quote is $1,400 for 100 ft, that is $14 per foot, matching the combined $6 and $8 rates in the tool. A number far above or below the others is worth a question about what it leaves out.
Common mistakes
- Using one rate for every site. A flat lawn and a slope full of tree roots are different jobs.
- Forgetting the outlet. The drain is only useful if the water has somewhere to go, and a long run to the street or a dry well adds length.
- Skipping the slope. Pipe laid level holds water instead of moving it.
- Leaving out repairs. Lawn, fence or walkway restoration is often quoted on its own line.
- Comparing quotes without the same scope. One bid may include fabric and an emitter and the next may not.
Related pages
To price the stone separately, see the French drain gravel calculator and the drain rock calculator. The drainage slope calculator helps you check the fall from one end of the trench to the other. For the dig itself, the excavation cost calculator covers machine work.
Frequently asked questions
How much does a French drain cost per foot?
It depends on your region, trench depth and whether a machine can reach the route. This calculator starts at $6 per foot for materials and $8 per foot for labor, which is $14 per foot. Treat those as placeholders and replace them with figures from two or three local quotes.
What is included in the material rate?
Perforated pipe, washed stone to fill the trench, and filter fabric to wrap the stone. Add a solid pipe for the outlet and a pop-up emitter or pop-up fitting if your quote lists them separately. If you want the stone quantity itself, use the French drain gravel calculator.
Why is labor usually the bigger number?
Someone has to dig a trench at a steady downhill slope, lay the pipe, place the stone and haul off the soil. Hand digging through roots, rock or a patio edge can take days. A mini excavator shortens the dig but adds machine rental or a higher hourly rate.
How steep should a French drain slope?
A drop of about 1 inch for every 8 feet of run, roughly 1 percent, is a common minimum for gravity flow. The pipe needs a place to empty, such as a lower part of the yard, a dry well or a storm outlet. Check local rules before you tie into anything public.
Does the estimate include permits or repairs?
No. The formula is only length times two rates. Permits, removing a section of fence, repairing a lawn after digging, and any extra pipe to a distant outlet should be added on top if they apply to your job.
Estimates only. Verify quantities with your supplier before purchasing.