Drain Rock Calculator 2026 - Estimate Tons & Cost for Drainage

For a standard French drain trench measuring 1 foot wide and 1 foot deep, you need approximately 0.037 cubic yards (or about 0.05 tons) of drain rock per linear foot. A 50-foot trench requires about 1.85 cubic yards or 2.5 tons. Always add 10% for waste and voids.

For deeper trenches at 18 inches deep and 12 inches wide, you need about 0.056 cubic yards per linear foot. That same 50-foot trench would require 2.78 cubic yards or approximately 3.9 tons of #57 drain rock. Use our French drain gravel calculator for custom dimensions.

One ton of drain rock typically equals 0.67 to 0.74 cubic yards, depending on the stone size and density. Standard #57 drain rock weighs about 1.35 to 1.5 tons per cubic yard, which means 1 cubic yard weighs between 2,700 and 3,000 pounds.

To convert your project volume to tons, multiply cubic yards by 1.4 (for #57 stone). For example, 5 cubic yards x 1.4 = 7 tons. Always check with your supplier for the exact weight per yard in your region, as limestone and granite have different densities. For other aggregate calculations, use our crushed stone calculator.

#57 crushed stone (3/4 inch to 1 inch) is the best size for most drainage projects like French drains and foundation backfill. The angular edges lock together for stability while leaving voids for water flow. Avoid pea gravel for drainage because the smooth edges cause it to shift and restrict water movement.

For heavy drainage applications like retention ponds or large dry wells, 1.5-inch drain rock provides even larger void spaces for high water volume. For septic drain fields, local codes typically mandate #57 stone or similar sized clean crushed rock. Decorative river rock should never be used for functional drainage. Calculate decorative stone needs with our river rock calculator.

In 2026, drain rock costs $45 to $85 per ton or $60 to $110 per cubic yard, depending on your location and the stone type. Delivery fees range from $50 to $150. For large projects over 10 tons, bulk pricing often drops to $35 to $55 per ton at the quarry.

Home improvement stores charge significantly more at $5 to $8 per 0.5 cubic foot bag (over $200 per ton). For any project requiring more than half a cubic yard, order bulk delivery from a local quarry to save 50% or more. Estimate your total project expenses using our excavation cost calculator.

A French drain should have 8 to 12 inches of drain rock below the perforated pipe and 2 to 3 inches above it. Total rock depth typically ranges from 12 to 18 inches. The trench itself should be 18 to 24 inches deep to accommodate the pipe, rock, and a protective fabric layer.

For heavy water flow areas, increase the rock depth below the pipe to 12 inches. Always place the pipe with holes facing down so water enters from the bottom. The fabric wrap should enclose both the rock and the pipe completely to prevent soil infiltration.

Yes, always wrap drain rock and the perforated pipe in non-woven geotextile fabric. The fabric prevents soil from clogging the voids between the rocks, which maintains water flow. Without fabric, silt and clay will fill the gaps within 1 to 3 years, making the drain useless.

Use non-woven filter fabric, not woven landscape fabric. Non-woven fabric allows water to pass through while blocking fine soil particles. Overlap fabric seams by at least 6 inches and wrap the rock completely, closing the top seam with landscape staples or zip ties.

Septic drain fields typically require 12 inches of drain rock below the pipe and 2 inches above. For a standard 3-foot wide trench, you need about 0.15 cubic yards per linear foot. A 100-foot trench requires 15 cubic yards or approximately 20 tons of drain rock.

Always verify depth and rock size with your local health department before ordering, as septic codes vary by county. Most codes require clean #57 stone with no fines. The rock must be washed to remove dust that could clog the soil absorption area. Calculate proper sub-base needs with our subbase calculator.

No, do not use pea gravel for drainage projects. Pea gravel is smooth and round, causing it to shift under pressure and compact tightly, which blocks water flow. Angular crushed stone like #57 drain rock is required because it interlocks for stability while leaving void spaces for water to pass through.

Pea gravel also migrates over time due to its smooth shape, creating uneven surfaces. For decorative above-ground applications like garden beds or walkways, pea gravel works well. But for any subsurface drainage, foundation backfill, or French drain, always use angular crushed stone. For landscape applications, reference the landscape rock calculator.