How Much Gravel Do I Need? Formula, Examples and Quick Chart
How to calculate how much gravel you need in cubic yards, tons and bags: the formula, worked examples for driveways, patios, paths and pea gravel, and a quick reference chart.
Nestiex Team ·
To work out how much gravel you need, you only need three measurements: length, width and depth. Multiply them together for the volume, convert to cubic yards, then to tons or bags depending on how your supplier sells it.
This guide gives you the formula, five worked examples and a quick chart. If you’d rather skip the maths, the gravel calculator on our homepage does it in one step.
The formula
Cubic yards = length (ft) × width (ft) × depth (in) ÷ 324
Dividing by 324 is the same as converting inches to feet (÷ 12) and then cubic feet to cubic yards (÷ 27).
Then convert as needed:
- Tons = cubic yards × 1.4. Dry gravel weighs about 105 lb/ft³, or 2,835 lb per cubic yard (Engineering ToolBox).
- Bags (0.5 ft³) = cubic yards × 54
- Bags (50 lb) = cubic yards × 57
Step by step: how to calculate how much gravel you need
- Measure the length and width of the area in feet. For irregular shapes, split the area into rectangles and add them up.
- Decide the depth in inches. See the depth table below.
- Multiply length × width × depth.
- Divide by 324 to get cubic yards.
- Add 5–15% for compaction and spreading losses. Driveway guides commonly suggest 10–15% (HomeGuide).
- Convert to tons or bags if your supplier sells that way.
Other shapes
- Circle: area = 3.14 × radius². A 10-ft-wide circular fire-pit area has radius 5 ft, so area = 3.14 × 25 = 78.5 sq ft.
- Triangle: area = ½ × base × height.
- L-shape: split it into two rectangles and add the areas.
Worked examples
1. Gravel driveway: 50 × 12 ft, 6 inches total
50 × 12 × 6 ÷ 324 = 11.1 cubic yards, which is 15.6 tons. With 10% extra: about 17 tons.
Most driveways are built in two layers: a crusher-run base plus a top layer. See how to build a gravel driveway and the gravel driveway calculator.
2. Pea gravel patio: 12 × 12 ft, 3 inches
12 × 12 × 3 ÷ 324 = 1.33 cubic yards, which is 1.87 tons or 72 bags of 0.5 ft³. See the pea gravel guide.
3. Garden path: 40 × 3 ft, 2 inches
40 × 3 × 2 ÷ 324 = 0.74 cubic yards, which is 1.04 tons or 40 bags of 0.5 ft³.
4. French drain: 50 ft × 1 ft wide, 18 inches of gravel
50 × 1 × 18 ÷ 324 = 2.78 cubic yards, which is 3.9 tons. See gravel for French drains.
5. Paver patio base: 20 × 10 ft, 6 inches
20 × 10 × 6 ÷ 324 = 3.7 cubic yards, which is 5.2 tons.
Unilock recommends extending the base past the paver edge by the base depth. A 20 × 10 ft patio with a 6-inch base is excavated to 21 × 11 ft (Unilock). That makes it 21 × 11 × 6 ÷ 324 = 4.3 yd³. See paver base explained.
Quick chart: cubic yards needed per 100 sq ft
| Depth | Cubic yards per 100 sq ft | Tons per 100 sq ft |
|---|---|---|
| 2 in | 0.62 | 0.86 |
| 3 in | 0.93 | 1.30 |
| 4 in | 1.23 | 1.73 |
| 6 in | 1.85 | 2.59 |
Multiply by your area ÷ 100. For example, 450 sq ft at 4 inches is 4.5 × 1.23 = 5.5 cubic yards.
How deep should the gravel be?
| Project | Typical depth | Source |
|---|---|---|
| Driveway (cars), total | 5–6 in minimum | HomeGuide |
| Driveway (heavy vehicles) | 8–12 in | HomeGuide |
| Paver base, patios and walkways | 4–8 in | Unilock |
| Paver base, driveways | 8–14 in | Unilock |
More detail in how much a yard of gravel covers.
How much pea gravel do I need?
The formula is the same. Pea gravel weighs about the same per yard as other dry gravel, so 1.4 tons per yard works for planning. For a 3-inch layer, one cubic yard covers about 108 sq ft. Use the pea gravel calculator for bags and cost.
Tips so you order the right amount
- Measure twice, and measure the depth after you excavate, not before.
- Round up. Running short means a second delivery fee. Extra stone is easy to use elsewhere.
- Check how your supplier sells. Convert yards to tons (× 1.4) or tons to yards (÷ 1.4) before you compare quotes. See the gravel cost guide.
- Account for compaction. Crusher run and road base shrink noticeably when compacted. The crushed stone calculator has a compaction allowance built in.
Frequently asked questions
How do I calculate how much gravel I need? Length (ft) × width (ft) × depth (in) ÷ 324 gives cubic yards. Multiply by 1.4 for tons.
How much gravel do I need for a 10 × 10 area? At 3 inches: 10 × 10 × 3 ÷ 324 = 0.93 yd³ (about 1.3 tons). At 4 inches: 1.23 yd³ (about 1.7 tons).
How much gravel do I need for a 100-ft driveway? For a 100 × 12 ft driveway at 6 inches: 100 × 12 × 6 ÷ 324 = 22.2 yd³, about 31 tons, before adding 10–15% extra.
How many tons of gravel do I need? Calculate cubic yards first, then multiply by 1.4.
Sources
- Engineering ToolBox, Dirt and Mud – Densities: engineeringtoolbox.com
- HomeGuide, How Much Does a Gravel Driveway Cost? (2026): homeguide.com
- Unilock, Do’s and Don’ts of Paver Installation: Base Preparation: unilock.com