Short title

French Drain Gravel & Stone Calculator

Calculate french drain gravel and crushed stone in cubic yards, tons, and bags. Includes pipe displacement deduction, fabric wrap, and compaction waste factors.

Lbl select preset
Sec trench dimensions
Lbl us units
50.0 Unit linear ft
12 Unit in
18 Unit in
Unit in
4 Unit in

Hint soil buried

Sec pipe bedding
3 Unit in
3"

Hint bedding

Lbl pipe savings banner

Desc pipe savings prefix 0.32 Unit tons (0.24 Unit cu yds) Desc pipe savings suffix $15.23 Desc on purchase orders

Sec aggregate density

1/2" to 1" angular stone. Gold standard for drainage voids and structural locking.

+10%
10%
Waste tightWaste recWaste rocky
12 Unit in
12"
$
$
Kpi gravel weight
2.89Unit tons
2.62 tonnes (5,782 lbs)
Kpi gravel volume
2.14Unit cu yds
1.64 m³ (58 cu ft)
Kpi bags required
116Unit bags
Lbl or 105 Lbl metric25 kg bags
Kpi total cost
$138.77
$2.78/linear ft
Svg trench title
Lbl live responsive
4" Svg topsoil backfill4.6" Svg pipe labelLbl trench width: 12" (30.5 cm)Lbl trench depth: 18" (45.7 cm)3" Svg bedding labelSvg geotextile wrap
Leg surface
Leg geotextile
Leg gravel
Leg pipe
Title bulk agg
Lbl net cu yds2.14 yd³
Lbl net tons2.89 Unit tons
Lbl metric tonnes2.62 tonnes
Lbl estimated bulk total$138.77
Title retail bags
Lbl50lb bags116 Unit bags
Lbl pallets required2.1 pallets
Lbl25kg bags105 Unit bags
Lbl estimated bag total$638.00
Title dump truck gauge
Truck pickup
3 Unit loads
Truck single
1 Unit loads
Badge optimal
Truck tandem
1 Unit loads
Truck tri
1 Unit loads

Title installation pipeline

1Step1 title

Step1 desc

2Step2 title

Step2 desc

3Step3 title

Step3 desc

4Step4 title

Step4 desc

Primary Metric
2.89 Unit tons (2.14 yd³)
+10% Badge waste
Efficiency / Capacity
250.0 sq ft (27.8 yd²)
12" Badge overlap
Net Output
2.9 yd³ (~3.1 t)
25% Badge swell

Client-Side Processing

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Technical Reference & Architecture Guide

French Drain Gravel & Stone Calculator Guide

Calculate french drain gravel and crushed stone in cubic yards, tons, and bags. Includes pipe displacement deduction, fabric wrap, and compaction waste factors.

French Drain Gravel & Stone Calculator Guide — Client-Side In-Memory Architecture & Data Flow
French Drain Gravel & Stone Calculator Guide — Client-Side In-Memory Architecture & Data Flow

Key Parameters & Controls

Trench Excavation WidthLinear distance in inches or centimeters

Minimum lateral clearance recommended by ASTM drainage guidelines is pipe outer diameter plus 6 to 8 inches (3 to 4 inches of aggregate surround on each side). Common bucket widths are 10, 12, or 16 inches.

Default: 12 inches (30.48 cm)
Trench Total DepthVertical distance in inches or centimeters

Total vertical cut from finished ground elevation to the excavated trench floor. Must satisfy both frost depth considerations and minimum 1% grade down to the discharge outlet.

Default: 18 inches (45.72 cm)
Perforated Pipe DisplacementCylindrical void volume deduction

The exact physical volume occupied by the drainage pipe conduit (e.g. 4-inch corrugated or PVC SDR-35). Subtracting pipe displacement prevents over-ordering gravel by 5% to 15% depending on trench depth.

Default: 4-inch Corrugated (0.087 cu ft per linear foot)
Aggregate Bulk DensityWeight per unit volume in pounds per cubic yard or tonnes per cubic meter

Standard washed #57 crushed limestone or granite ranges from 2,600 to 2,800 lbs per cubic yard (average 2,700 lbs or 1.35 short tons). Moisture content and compaction can increase weight by 5% to 8%.

Default: 2,700 lbs/yd³ (1.60 tonnes/m³)
Geotextile Overlap AllowanceEnvelope wrap perimeter addition in inches

The width of non-woven filter fabric required to completely encapsulate the aggregate core with a minimum 12-inch top lap to prevent soil fine infiltration while sustaining 90-140 GPM/sq ft permittivity.

Default: 12 inches (30.48 cm)
Soil Bulking Expansion FactorVolumetric expansion multiplier

Undisturbed native soil expands upon excavation due to air void incorporation. Compacted clay swells by 25% to 35%, loam by 20%, and sand by 15%, dictating necessary spoil haul-away container volume.

Default: 1.25 (25% spoil expansion)

Pro Tips & Best Practices

Always Orient Perforated Pipe Holes Downward at 4 and 8 O'Clock

Never install perforated drainage pipe with holes facing up. Groundwater enters a French drain as the subterranean water table rises from the bottom of the trench. Positioning perforations downward allows water to enter the pipe at its lowest elevation and flow away immediately before filling the surrounding stone cavity.

Use Non-Woven Geotextile Fabric, Never Woven Landscape Weed Barrier

Standard woven weed barriers are tightly stitched to block light and have poor water permittivity (less than 15 GPM/sq ft), which causes fine clay particles to glaze the fabric surface and blind the system within 2 to 3 years. Specify 4-oz or 6-oz needle-punched non-woven geotextile with a water flow rate exceeding 100 GPM/sq ft.

Maintain Minimum 1/8-Inch Drop Per Foot (1% Grade) for Self-Cleaning

A flat trench will collect water but rely solely on hydrostatic head pressure, causing silt and fine sediment to settle in pipe corrugations. Maintaining a minimum 1% slope (1 inch drop every 8 feet, or 12.5 inches per 100 feet) ensures gravity creates self-scouring velocity (minimum 2 feet per second).

Select Angular #57 Washed Crushed Stone Over Rounded Pea Gravel

Uniform 1/2-inch to 1-inch angular crushed stone (AASHTO #57) creates inter-locking structural matrix stability with 40% open pore space that will not shift under ground settlement or vehicle traffic, whereas small 3/8-inch rounded pea gravel migrates easily and clogs pipe slots.

Common Gotchas & Troubleshooting

⚠️Gravel Deficit: Running short of gravel by 1 to 2 tons near the end of the trench run

Excavator bucket teeth, jagged trench walls, and soil compaction under heavy aggregate create 10% to 15% hidden void volume beyond pure nominal geometric calculations. Always apply a 10% waste and compaction multiplier on straight residential runs, and 15% if the trench winds through uneven tree roots or rocky subgrades.

⚠️Water Surfacing Above Drain: Standing water pooling directly over the top of the French drain

Occurs when topsoil backfill layer is too thick (exceeding 6 inches) or consists of heavy, unamended impermeable clay that prevents surface water percolation into the gravel envelope. Replace topsoil backfill with sandy loam, or extend the gravel envelope completely flush to the surface as an exposed gravel swale.

⚠️Crushed or Deformed Corrugated Pipe Under Lawnmower or Light Vehicle Loads

Thin single-wall corrugated polyethylene pipe (ADS) has low crush resistance and deforms when buried under less than 12 inches of cover. In driveways, walkways, or shallow trenches (under 18 inches depth), upgrade to rigid ASTM D2729 or SDR-35 perforated PVC pipe embedded in a minimum 3-inch compacted gravel cradle.

⚠️Excess Excavation Dirt Piles: Underestimating spoil soil disposal volume

Remember that dirt expands by roughly 25% to 30% when dug out of the ground. Because the French drain replaces excavated native earth with gravel and pipe, nearly 80% of the dug-out dirt cannot be returned to the trench and must be hauled off-site or graded elsewhere on the property.

Frequently Asked Questions

How do I calculate how much gravel I need for a French drain?▼

Multiply trench length (ft) by trench width (ft) by gravel depth (ft) to calculate total trench volume in cubic feet, subtract the cylindrical volume of your pipe (pi * radius^2 * length), add a 10% compaction factor, then divide by 27 to obtain cubic yards. Multiply cubic yards by 1.35 to get short tons of standard #57 crushed stone.

How many tons of gravel are needed for a 50 ft or 100 ft French drain?▼

For a standard 12-inch wide by 18-inch deep trench with a 4-inch pipe and 4 inches of soil cover: a 50-foot French drain requires approximately 1.9 cubic yards (2.6 tons) of #57 gravel; a 100-foot French drain requires approximately 3.8 cubic yards (5.2 tons) of #57 gravel, assuming a standard 10% overage buffer.

Should I use crushed stone or pea gravel for a French drain?▼

Use angular AASHTO #57 washed crushed stone (1/2-inch to 1-inch) rather than rounded pea gravel. Angular crushed stone locks together mechanically to maintain structural void spaces (40% porosity) that resist heavy ground pressure, while rounded pea gravel shifts, compacts, and migrates through fabric folds or pipe perforations.

Do French drain pipe holes face up or down?▼

Drainage pipe holes must face down toward the trench floor. Water enters a French drain from subterranean hydrostatic pressure rising up from below; positioning perforations downward at the 4 and 8 o'clock positions allows water to enter the pipe immediately at the lowest invert elevation and escape downhill.

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