How this gravel calculator works
This gravel calculator estimates how much material you need by computing the volume of your project area and multiplying it by the bulk density of gravel. You can work in either US/imperial or metric units and switch between them at any time.
Step 1 – Choose the area shape
- Rectangle / square – for driveways, patios, parking pads, and most paths.
- Circle – for circular patios, tree rings, or round pads.
- Border / trench – for garden edging, French drains, or long narrow strips.
- Multiple areas – if you already know the total volume of several shapes combined.
Step 2 – Enter dimensions and depth
Enter length, width, and depth in your preferred units. The calculator automatically converts everything to a consistent unit system internally.
Rectangle / square volume
For a rectangular area:
$$ V = L \\times W \\times D $$
where:
- \(L\) = length
- \(W\) = width
- \(D\) = depth (thickness of gravel layer)
Circle volume
For a circular area with diameter \(d\):
$$ A = \\pi \\left(\\frac{d}{2}\\right)^2 $$
$$ V = A \\times D $$
Border / trench volume
For a long narrow strip:
$$ V = L \\times W \\times D \\times n $$
where \(n\) is the number of identical runs.
Step 3 – Convert volume to cubic yards or cubic meters
The calculator converts the raw volume to common units:
- Cubic yards (yd³) – standard for US gravel suppliers.
- Cubic meters (m³) – standard in metric markets.
- Cubic feet (ft³) – useful for small projects.
Key volume conversions
- \(1\\,\\text{yd}^3 = 27\\,\\text{ft}^3\)
- \(1\\,\\text{m}^3 \\approx 1.308\\,\\text{yd}^3\)
- \(1\\,\\text{ft}^3 \\approx 0.03704\\,\\text{yd}^3\)
Step 4 – Apply gravel density to get weight
Gravel is sold by weight (tons or tonnes) or by volume (cubic yards or cubic meters). To convert volume to weight you need the bulk density of the material.
Typical densities:
- Pea gravel: ~1.35 tons/yd³ (~1,600 kg/m³)
- Crushed stone (3/4"): ~1.5 tons/yd³ (~1,800 kg/m³)
- Dense road base: ~1.7 tons/yd³ (~2,000 kg/m³)
Weight from volume
Using US units:
$$ \\text{Weight (tons)} = V_{yd^3} \\times \\rho_{\\text{tons/yd}^3} $$
Using metric units:
$$ \\text{Weight (kg)} = V_{m^3} \\times \\rho_{\\text{kg/m}^3} $$
Step 5 – Add waste and compaction allowance
Real projects are never perfectly flat. Gravel settles and compacts, and you’ll lose some material when trimming edges. A 5–10% allowance is common:
$$ V_{\\text{with waste}} = V_{\\text{net}} \\times (1 + w) $$
where \(w\) is the waste fraction (e.g. 0.05 for 5%).
Worked example: gravel for a driveway
Suppose you have a driveway that is 40 ft long and 12 ft wide, and you want 6 inches of compacted gravel.
- Convert depth: 6 in = 0.5 ft.
- Volume in ft³: \(V = 40 \\times 12 \\times 0.5 = 240\\,\\text{ft}^3\).
- Convert to yd³: \(240 / 27 \\approx 8.89\\,\\text{yd}^3\).
- Weight (using 1.5 tons/yd³): \(8.89 \\times 1.5 \\approx 13.3\\,\\text{tons}\).
- Add 5% waste: \(13.3 \\times 1.05 \\approx 14.0\\,\\text{tons}\).
The calculator performs all of these steps instantly and also tells you the approximate number of bags.
Typical gravel depths by project type
| Project type | Recommended depth | Notes |
|---|---|---|
| Driveway / parking area (new) | 6–8 in (15–20 cm) | Often built in layers: base + top course. |
| Driveway top-up | 2–3 in (5–8 cm) | For refreshing existing gravel. |
| Garden path / walkway | 2–4 in (5–10 cm) | Use smaller gravel for comfortable walking. |
| Patio base under pavers | 4–6 in (10–15 cm) | Plus sand or screening layer on top. |
| French drain / trench | Varies | Follow engineer or manufacturer specs. |
FAQ
How do I calculate how much gravel I need?
Measure the area, compute the volume (length × width × depth), convert to cubic yards or cubic meters, then multiply by the gravel density to get tons. This calculator automates all conversions and lets you adjust for waste and compaction.
How many tons of gravel are in a cubic yard?
Most common gravel and crushed stone weighs between 1.3 and 1.7 short tons per cubic yard. A widely used average is 1.5 tons/yd³, which is the default in this tool. If your supplier gives a specific density, choose “Custom density” and enter it.
How many bags of gravel do I need?
Once you know the total weight, divide by the weight per bag. For example, if you need 2,700 lb and your bags are 50 lb each, you need 2,700 ÷ 50 = 54 bags. The calculator does this for up to three bag sizes at once.
Should I compact gravel before measuring depth?
Depth is usually specified as compacted thickness. If you measure loose gravel, it will compact down, so you may need to order more. Using a 5–10% waste/compaction allowance is a simple way to account for this.
Can I use this for crushed stone, limestone, or decorative rock?
Yes. The math is the same for any loose aggregate. Just make sure the density you use matches the material (your supplier can provide a value in tons/yd³ or kg/m³).