French Drain Gravel Calculator

Check whether your drain actually needs a gravel order

This calculator models a rectangular gravel envelope around a circular pipe. It is useful after the drainage system, outlet and cross-section have been selected. It does not decide whether a French drain will solve the water problem.

Two systems, different shopping lists

NDS EZflow is a manufacturer example of a gravel-free system using engineered aggregate bundles. Its existence matters to the estimate: a prefabricated aggregate assembly is not simply bare pipe inside the loose-gravel envelope modeled below. This example is not a product endorsement or a suitability decision for your site.

• Specified loose-gravel system: obtain the required aggregate and filtration detail, then enter the gravel envelope and pipe outside diameter. Compare bags and bulk for that same aggregate.
• Specified prefabricated system: order the required assembly configuration, lengths, connections and outlet components from its installation detail. Do not add this page's full gravel result or four-sided fabric allowance unless the selected design separately requires those materials.
• System or outlet unresolved: hold the order and confirm the drainage plan. Extra gravel is not a substitute for an appropriate discharge arrangement or a capacity assessment.

Separate the shopping list before comparing prices

In the 50 ft loose-gravel example below, the result is approximately 2.8778 cu yd before supplier minimums and increments. That number is not a gravel requirement for every 50 ft prefabricated drain. Nor can 50 ft alone determine the number of bundles: configuration, usable lengths and connection details must come from the chosen system. Compare complete feasible systems rather than a gravel-only subtotal against a bundle price.

1. Record the selected detail and exact aggregate or assembly code. Confirm whether pipe and filter components are included or separate.
2. For loose gravel, use the supplier-order example and enter the seller's bag yield, minimum, increment and delivery. Keep pipe, fittings, filtration, outlet and excavation on separate lines.
3. Attach the selected specification to the downloaded estimate. The download records geometry and prices, not approval of the drainage system.
4. Use the quote checklist to resolve missing items and access before accepting a price. Do not assume a generic landscape fabric is the specified drainage filter.

System-selection reference checked November 7, 2026. Quantity planning only; excavation safety, utility clearance, local requirements and drainage design must be resolved separately.

Material-choice review: November 2, 2026. These are planning choices, not a site inspection or a drainage specification.

Turn drain gravel volume into a supplier order

The main result now includes any entered bulk minimum and buying increment. The bag alternative uses the gravel volume after pipe displacement and allowance, not the larger bulk minimum. Bulk and bags are alternatives: do not add their quantities or totals together. Set the existing price per cubic yard for bulk; enter the separate per-bag price for bags. Cost totals appear only for options with a positive material price.

A 50 ft drain: 3 cubic yards or 156 bags

For the editable 50 ft run, 12 in wide × 18 in gravel envelope, 4 in pipe outside diameter and 10% extra, the material need is approximately 2.8778 cu yd. With an illustrative 2 cu yd minimum and quarter-yard increments, buy 3 cu yd. The bag alternative at 0.5 cu ft per bag is 156 bags. If the supplier minimum were 4 cu yd, bulk would become 4 cu yd but the bag requirement would remain 156.

At hypothetical prices of $60 per cu yd plus $80 bulk delivery, the 3 cu yd option totals $260. At $5 per bag with $0 entered bag delivery, bags total $780. These are arithmetic examples, not local prices. Compare the same specified aggregate and confirm any taxes, unloading or handling before choosing. No density or tonnage conversion is assumed.

Keep the rest of the drain order separate

The 50 ft pipe run does not include fittings, outlet hardware or buying-length rounding. The 300 sq ft fabric figure is a four-sided wrap with a 12 in longitudinal overlap, not a roll count; ends and seams require a separate approved layout. This calculation does not choose pipe grade, aggregate, filtration detail, drainage capacity or outlet. Measure the gravel envelope, excluding any soil cover. Do not use the full excavation depth when part will be filled with soil.

Download estimate retains the measurements, bag yield, supplier minimum/increment, separate prices and delivery inputs. A zero delivery value is not proof of free delivery. Tax, excavation, labor, pipe, fabric and other unentered items are excluded from gravel totals.