System: US (Imperial)
Fill method: Components
Waste: 5%
Pipes: 1
Inputs
Switching updates field units and density meaning.
Covers spillage, trench irregularities, bulking.
tons/yd³
Typical drain rock ≈ 1.3–1.5 tons/yd³ (US) or 1500–1700 kg/m³ (SI).
lb
Change to 25 for 25‑kg bags in SI.
Results
Calculated fill depth: — in
Trench geometric volume
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Pipe displacement volume
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Net rock volume (with waste)
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Estimated weight
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Estimated bags
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Rounded up to whole bags.
Key conversions
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| Metric | Value | Units |
|---|
Example Data Table
Load any row to prefill the inputs, then hit Calculate.
| Scenario | System | Length | Width | Bedding | Pipe O.D. | Cover | Pipes | Density | Waste | Mode | Action |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Yard perimeter run | US | 80 ft | 18 in | 3 in | 4 in | 6 in | 1 | 1.4 tons/yd³ | 7% | Components | |
| Basement wall relief | US | 40 ft | 12 in | 2 in | 4 in | 8 in | 2 | 1.35 tons/yd³ | 5% | Components | |
| Garden bed drainage | SI | 20 m | 30 cm | 5 cm | 10 cm | 10 cm | 1 | 1600 kg/m³ | 6% | Direct |
Formulas Used
- Fill depth (components mode) =
bedding + pipe_OD + cover - Trench volume =
length × width × fill_depth - Pipe displacement =
pipes × length × π × (OD/2)2 - Net rock volume =
max(Trench − Pipe, 0) - Add waste =
Net × (1 + waste%/100) - Weight (US) =
yd³ × density(tons/yd³); Weight (SI) =m³ × density(kg/m³) / 1000(tonnes) - Bags =
Weight_in_mass_units ÷ bag_weight(rounded up)
Widths/depths are internal to rock area. Pipe O.D. includes wall thickness. Bulk density already accounts for voids between stones.
How to Use This Calculator
- Select US or Metric, then choose your fill method.
- Enter trench length and inside width. Add bedding, pipe O.D., cover, or a direct fill depth.
- Set pipe count, waste percentage, rock density, and bag size.
- Click Calculate to see volumes, weight, and bags.
- Use Download CSV or Download PDF to save the summary.
- Optionally toggle Remember inputs to store values locally on this device.
FAQs
Yes. Displacement equals pipe outer volume along the trench, multiplied by pipe count. This is subtracted from trench volume before waste is applied.
Common bulk densities range 1.3–1.5 tons/yd³ (US) or 1500–1700 kg/m³ (SI). Ask your supplier for their stockpile value to improve accuracy.
Fabric thickness is negligible for quantity. Do include its presence around the rock for performance, but it does not materially change rock volume.
Yes. If you are not filling to grade with rock, reduce the fill depth or choose the components mode to model the exact cover above the pipe.
Typical projects allow 5–10% for irregular trenches, bulking, and spillage. Use higher waste when trench walls collapse or rock segregates during placement.
Enter the outer diameter. For corrugated drains, the nominal size often approximates O.D., but verify manufacturer data for accuracy.
No. Supplier bulk density already includes voids. Buy by volume/weight using that bulk density; the void space is inherent in the material specification.
French Drain Rock Quantity — Per‑Foot Quick Reference
Auto‑computed from current pipe count, pipe O.D., waste, and density.
| Inside Width | Fill Depth | Net Rock per 1 ft | Net Rock per 1 m | Weight per 10 ft | Weight per 3 m |
|---|
French Drain Rock Quantity — Fill Depth Sensitivity
Impact of varying fill depth for the current trench width.
| Fill Depth | Net Rock per 1 ft | Net Rock per 1 m | Weight per 10 ft | Weight per 3 m |
|---|
French Drain Material Data — Densities & Conversions
Common Bulk Densities (reference)
- Drain rock (washed angular): 1.3–1.5 tons/yd³; 1500–1700 kg/m³
- Pea gravel: 1.2–1.4 tons/yd³; 1400–1650 kg/m³
- Sand (damp): 1.3–1.6 tons/yd³; 1600–1900 kg/m³
Ask your supplier for a project‑specific bulk density for best accuracy.
Useful Conversions
- 1 yd³ = 27 ft³ = 0.7646 m³
- 1 m³ = 1.3079 yd³ = 35.3147 ft³
- 1 ton (US) = 2000 lb = 0.9072 tonnes
- 1 tonne = 1000 kg = 1.1023 tons (US)
- 1 in = 2.54 cm; 1 ft = 0.3048 m