Enter project details
Example data table
| Scenario | Area | Depth | Density | Waste | Estimated quantity |
|---|---|---|---|---|---|
| Garden bed (imperial) | 20 ft × 8 ft | 2.5 in | 100 lb/ft³ | 10% | ~1.37 yd³, ~1.85 tons |
| Pathway (imperial) | 30 ft × 4 ft | 2.0 in | 105 lb/ft³ | 8% | ~0.92 yd³, ~1.56 tons |
| Round bed (metric) | Diameter 4.0 m | 6 cm | 1650 kg/m³ | 12% | ~1.10 m³, ~1.82 tonnes |
Example quantities are illustrative; suppliers and compaction can vary.
Formula used
1) Area
- Rectangle: Area = Length × Width
- Circle: Area = π × (Diameter ÷ 2)²
2) Volume
Volume = Area × Depth
- Imperial: convert depth inches to feet (Depthft = Depthin ÷ 12)
- Metric: convert depth centimeters to meters (Depthm = Depthcm ÷ 100)
3) Weight or mass
Weight/Mass = Volume × Density
4) Waste allowance
Adjusted quantity = Base quantity × (1 + Waste% ÷ 100)
5) Ordering units
- Imperial cubic yards: yd³ = ft³ ÷ 27
- Imperial tons (short): tons = lb ÷ 2000
- Metric tonnes: tonnes = kg ÷ 1000
How to use this calculator
- Select your unit system and the shape of the area.
- Enter dimensions and the planned rock depth.
- Enter rock density if you know it; otherwise use a typical value.
- Set a waste factor to cover uneven grades and trimming losses.
- Choose bulk or bags, then add pricing if you want a cost estimate.
- Click Calculate and use the CSV or PDF buttons for records.
For driveways, confirm supplier minimum loads and delivery access.
Practical guidance for decorative rock planning
1) Set a depth that matches stone size
Depth drives both appearance and stability. For 3/8–3/4 inch gravel, 2 inches hides fabric and provides color. For 1–2 inch river rock, 3–4 inches reduces visible gaps. On slopes, add 0.5–1 inch to counter migration and raking loss.
2) Measure area with repeatable field methods
Rectangles are fastest: length times width. For curved beds, break the space into smaller rectangles and circles, then add results. A checklist helps: measure along the border, note obstacles, and recheck units. Small measurement errors compound when depth is applied.
3) Convert volume into ordering units
Volume is area times depth. In imperial jobs, cubic yards equal cubic feet divided by 27, so a bed measuring 160 ft² at 2 inches is about 0.99 yd³ before waste. In metric, cubic yards are useful for some suppliers, but cubic meters stay most direct.
4) Use density to anticipate hauling weight
Density links volume to weight, affecting truck capacity and fees. Many gravels fall near 95–110 lb/ft³ (about 1500–1750 kg/m³), while lava rock can be far lighter. If your vendor lists “pounds per cubic yard,” enter an equivalent density for better ton estimates.
5) Apply a waste factor for real sites
Waste covers spillage, trimming, voids, and compaction. Clean, straight runs with edging may need 5–8%. Curves, steps, and planting pockets often need 10–15%. If you are topping up an existing bed, waste can drop, but expect extra for cleanup and blending.
6) Decide between bulk delivery and bags
Bulk is cost‑efficient for larger areas, but requires access, staging space, and wheelbarrow routes. Bags reduce mess and are ideal for rooftops, courtyards, and small repairs. The calculator shows bag counts from weight, so you can compare bulk quotes to retail packaging quickly.
7) Build a complete cost estimate
Material cost is only one line item. Add delivery charges, minimum load fees, and labor or equipment rental for spreading. If you only know price per yard, use that; if you know price per ton, use weight. Comparing both often reveals the best supplier for your schedule.
8) Verify assumptions before purchasing
Confirm stone size, moisture condition, and whether pricing is for loose or screened material. Ask about compaction expectations and return policies. Then walk the site once more to check for grade changes and hidden corners. Accurate inputs plus waste margin prevent last‑minute shortages.
FAQs
1) What depth is best for decorative rock?
Most beds look good at 1.5–3 inches for small stone, and 3–4 inches for larger rock. Use thicker layers on slopes to reduce exposed fabric and thin spots.
2) Should I order by tons or cubic yards?
Cubic yards match coverage because they come from volume. Tons help with delivery limits and pricing. If possible, calculate both, then use the unit your supplier sells.
3) Why does the calculator ask for density?
Density converts volume into weight, which affects tons, bags, and hauling. Different rock types vary widely, so using a supplier value improves accuracy and reduces surprise fees.
4) How much waste should I add?
Use 5–8% for simple rectangles with edging, 10–15% for curves and uneven grades, and up to 20% for very irregular shapes or deep installations with settling.
5) How do I estimate bag counts?
The tool divides adjusted weight by bag weight and rounds up. Bag coverage also depends on rock size, so treat bag counts as an ordering guide and keep one extra bag for touch‑ups.
6) Does compaction change the result?
Yes. Loose rock occupies more volume than compacted rock after raking and walking. The waste factor helps cover compaction and small voids, especially for angular stones that lock together.
7) Can I use this for driveways?
Yes for top layers, but driveways often need a structured base, thicker depth, and compaction. Confirm local recommendations and consider drainage, geotextile, and aggregate gradation.