How Much Gravel Do I Need? The Ultimate Calculator Guide
Ordering gravel is not like ordering pizza — you cannot just call and say "a large, please." Order too little and your project grinds to a halt while you wait for a second delivery. Order too much and you are paying for material that sits in a pile in your yard. Getting the quantity right is one of the most important parts of any aggregate project, and it is simpler than you think once you understand the formula.
The Formula, Explained Simply
Every gravel calculation comes down to three numbers: length, width, and depth. Here is the formula in plain English:
The Gravel Formula
Length (ft) x Width (ft) x Depth (in) / 12 = Cubic Feet
Cubic Feet / 27 = Cubic Yards
Cubic Yards x 1.4 = Tons (for most gravel)
The 1.4 multiplier is the average density of gravel in tons per cubic yard. This varies by material — see the coverage chart below for specific densities.
Let's Walk Through an Example
Say you need to cover a 20-foot by 30-foot patio area with 3 inches of pea gravel:
- Step 1: 20 x 30 x (3/12) = 150 cubic feet
- Step 2: 150 / 27 = 5.56 cubic yards
- Step 3: 5.56 x 1.4 = 7.78 tons
- Step 4: Add 10% overage: 7.78 x 1.1 = 8.56 tons. Round up to 8.6 tons.
Quick Reference Chart for Common Projects
| Project | Typical Dimensions | Depth | Cubic Yards | Tons |
|---|---|---|---|---|
| Single-car driveway | 10 x 40 ft | 4" | 4.9 | 6.9 |
| Two-car driveway | 20 x 40 ft | 4" | 9.9 | 13.8 |
| Patio | 12 x 12 ft | 3" | 1.3 | 1.9 |
| Walkway | 3 x 30 ft | 3" | 0.8 | 1.2 |
| French drain (50 ft) | 1 x 50 ft | 18" | 2.8 | 3.9 |
| Small parking area | 20 x 20 ft | 6" | 7.4 | 10.4 |
Why You Should Always Order 10% Extra
We recommend ordering 10 percent more material than your calculated amount. Here is why:
- Compaction loss: Gravel compacts 5 to 10 percent when you run a plate compactor or roller over it. What looked like 4 inches of material becomes 3.5 inches.
- Uneven subgrade: Even if you grade your subgrade carefully, there are always low spots and dips that eat up extra material.
- Spreading loss: Some material migrates beyond your project boundaries during installation, especially on edges without containment.
- Second delivery costs: If you run short, a second delivery typically costs as much as the first in delivery fees — often $75 to $150 for a small top-up load.
Pro tip: Running short is always more expensive than having a small pile left over. A leftover half-ton of gravel is useful for future fill-ins and maintenance. A half-ton shortfall means a $150 delivery for $30 worth of material.
Coverage by Material Type
Different materials have different densities, which means 1 cubic yard of each material weighs a different amount in tons. Here is a reference chart for common materials:
| Material | Tons per Cubic Yard | Sq Ft per Ton at 2" | Sq Ft per Ton at 4" |
|---|---|---|---|
| Crushed Limestone | 1.5 | 108 | 54 |
| Pea Gravel | 1.4 | 116 | 58 |
| Flex Base | 1.5 | 108 | 54 |
| River Rock | 1.35 | 120 | 60 |
| Decomposed Granite | 1.4 | 116 | 58 |
| Fill Dirt | 1.1 | 147 | 74 |
| Sand | 1.35 | 120 | 60 |
| Crushed Concrete | 1.3 | 125 | 62 |
Calculate Your Project Now
Enter your project dimensions below and our calculator will do the math for you — including the 10 percent overage buffer and estimated cost.
Quantity Calculator
Enter your project dimensions
Calculating for Irregular Shapes
If your project area is not a simple rectangle, break it into rectangles and calculate each section separately. For example, an L-shaped driveway can be split into two rectangles. Add the cubic yards together for your total order.
For circular areas (like a fire pit surround), use: radius x radius x 3.14 x depth (in feet) / 27 = cubic yards.