French Drain Gravel Calculator: Yards, Tons & Bags

La mayoría de los proveedores venden french drain gravel por yarda cúbica. Para convertir el área a yardas cúbicas, usa esta fórmula:

Nuestra calculadora también multiplica el resultado por 1.4 toneladas/yd³ (la densidad estándar de french drain gravel) para mostrar el peso estimado.

A French drain gravel calculator converts your trench dimensions into orderable quantities: cubic yards for bulk delivery, tons for quarry pricing, and bags for small repairs. The volume formula is (Length in feet x Width in feet x Gravel Depth in feet) / 27 = Cubic Yards, and tonnage follows from the density of washed stone: Cubic Yards x 1.4 = Tons. A 50-foot trench, 12 inches wide, with 18 inches of gravel: (50 x 1 x 1.5) / 27 = 2.78 cubic yards, or 3.9 tons. Note that the depth in the formula is the gravel depth only, not the full trench depth: the pipe and its bedding displace stone, and overcounting with the full depth is the most common estimating error.

Gravel selection makes or breaks the drain. Washed 3/4-inch angular stone, known as #57 in the aggregate trade, is the specified material because its sharp edges interlock into a stable bed while leaving about 40% void space between stones for water to travel through. The washing matters as much as the size: unwashed stone carries stone dust and fines that settle into the voids and choke flow within a season or two. Pea gravel looks tidy but its rounded shape migrates under load and works its way into the pipe perforations. Crusher run is worse: it compacts into a near-impermeable layer, which is the exact opposite of what a drain needs. When the quarry asks what the stone is for, saying French drain gets you washed #57 without further discussion. It also keeps your estimate honest: a French drain gravel calculator assumes clean angular stone at 1.4 tons per yard, and substituting a denser material throws the tonnage off.

Trench geometry follows a few fixed rules. Width runs 9 to 12 inches for a standard 4-inch perforated pipe: enough room for gravel on both sides of the pipe, narrow enough to dig by hand with a trenching shovel. Depth is 18 to 24 inches for yard drainage and down to footing level for foundation drains. The pipe bed gets 2-3 inches of compacted gravel, then the pipe itself, then 6-12 inches of cover stone above it before soil goes back. The critical number is slope: a 1% grade, which is 1/8 inch of fall per foot of trench. Flatter than that and water sits instead of flowing, letting sediment settle in the pipe; steeper is fine but rarely achievable across a flat yard. Check slope with a 4-foot level and a tape as you dig, not after the gravel is in.

Assembly order matters once the gravel math is done. Line the trench with non-woven geotextile fabric first, leaving enough extra to fold over the top burrito-style with a 12-inch overlap. Place the bedding gravel and compact it lightly, set the perforated pipe with the holes facing down (water rises into the pipe from below through the stone bed; holes-up lets silt wash straight in), and recheck slope. Fill with washed stone to about 6 inches below finished grade (the depth your French drain gravel calculator used for its volume), fold the fabric over the stone, then top with soil and sod or a shallow decorative gravel strip. Every fabric penetration, including where downspouts tie into the system, gets overlapped or sealed: one unprotected joint lets in enough silt to start the clogging process.

Order gravel by the ton for any trench over about 30 feet: bulk delivery at $40 to $65 per ton beats retail bags by a factor of three once you pass two tons. Bags make sense only for short repairs under 20 feet, where a half-cubic-foot bag at $4 to $6 each is cheaper than a quarry delivery fee. Quarries sell by the ton with a 2 to 3-ton minimum for delivery, so combine the drain stone with any other aggregate your project needs. Run the final trench numbers through a French drain gravel calculator, then add an extra half-ton to the order: running short mid-trench leaves pipe sitting exposed while you wait on a second truck, and the delivery fee on a small second load wipes out any savings from ordering tight.