Calculate French drain gravel volume and tons from trench dimensions, pipe diameter, gravel depth, density and waste. Plan bulk stone before ordering.
Enter your measurements and material details.
Use the gravel-filled depth, not total excavation depth if part of the trench contains topsoil, cover material or another layer.
French drains use a significant volume of stone because the pipe occupies only part of the trench. This calculator estimates the gravel-filled trench volume and subtracts the approximate pipe displacement before converting the result into cubic yards and tons.
Measure the trench length along its actual route. Enter the internal width of the excavation and the depth that will be filled with gravel. The pipe is modeled as a cylinder, so fittings and slight trench variation are handled by the waste allowance rather than detailed geometry.
It depends on trench width, gravel depth, pipe diameter and length. The calculator converts those dimensions into yards and tons.
The pipe occupies space that otherwise would be filled with gravel.
Use the tons-per-cubic-yard figure from the supplier when available.
Yes. Irregular excavation and settlement can increase the actual quantity.
No. Use the landscape fabric calculator for fabric coverage.
Using the example inputs shown in the calculator — Trench length (ft) = 60, Trench width (in) = 12, Gravel-filled depth (in) = 18, Pipe outside diameter (in) = 4, Gravel density (tons/yd³) = 1.4 — the result is 3.45 cubic yards. This demonstrates the formula with a complete set of numbers rather than a hidden assumption.
The result breakdown also shows Approx. tons: 4.83 tons; Adjusted cubic feet: 93.2 ft³. Replace the example values with field measurements and the exact product coverage, yield or package size you plan to buy.
For this french drain gravel calculator, the inputs with the greatest practical effect are trench length, trench width and gravel-filled depth. Recalculate when any of those change; do not reuse a result from a different room, run, layer depth or product specification.
These quick examples use the same calculator formula and the assumptions stated in each row. They are useful for scale checks; use your own measurements for ordering.
| Example | Calculated result |
|---|---|
| 50 ft drain, 12 in wide × 18 in deep | 2.88 cubic yards |
| 100 ft drain, 12 in wide × 18 in deep | 5.76 cubic yards |
| 50 ft drain, 18 in wide × 24 in deep | 5.93 cubic yards |
A useful french drain gravel estimate begins with dimensions taken from the actual project. Small measurement errors can become significant when they are repeated across many boards, joints, courses, bags or rolls. Record the dimensions you used and keep net geometry separate from the purchase allowance so the result can be checked later.
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