How Much Gravel Do I Need?
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Multiply length x width x depth (all in feet) to get cubic feet, divide by 27 for cubic yards, then multiply by the product's density and divide by 2,000 to get tons. A 20 ft x 10 ft path at 4 inches deep needs about 2.47 cubic yards, or roughly 3.1-3.5 tons depending on the stone.
Gravel is sold by volume (cubic yards) or by weight (tons). Both come from the same starting point: the volume of the space you are filling, converted using the density of the specific product you order.
Key takeaways
- Volume = length x width x depth, with depth converted from inches to feet by dividing by 12.
- Cubic feet / 27 = cubic yards, the unit most bulk suppliers price by.
- Loose gravel density is commonly 95-125 lb per cubic foot, so tonnage estimates vary by product.
- Add 5-10% for waste and more for compacted base layers.
Run the numbers with the Gravel Calculator.
Step 1 — measure in one consistent unit
Volume = length x width x depth. Depth is usually given in inches while length and width are in feet, so convert depth to feet by dividing by 12. A 20 ft x 10 ft area at 4 inches deep is 20 x 10 x 0.333 = 66.7 cubic feet.
Divide cubic feet by 27 to get cubic yards, the unit most bulk suppliers quote. 66.7 / 27 = 2.47 cubic yards.
Step 2 — choose a depth that suits the job
- Garden paths and decorative beds: 2-3 inches.
- Walkways over a prepared base: 3-4 inches.
- Driveway top layer: 3-4 inches over a compacted base.
- Full new driveway build-up: often 8-12 inches total across base and top layers.
Step 3 — convert volume to tons
Tons = cubic feet x density (lb per cubic foot) / 2,000. Loose gravel commonly falls between roughly 95 and 125 lb per cubic foot depending on stone size, mineral type, moisture and compaction.
- Take the 66.7 cubic foot example above.
- At a density of 105 lb/ft³ (a common crushed-stone estimate): 66.7 x 105 = 7,003.5 lb.
- Divide by 2,000: 7,003.5 / 2,000 ≈ 3.5 tons.
- At a lighter density of 95 lb/ft³: 66.7 x 95 / 2,000 ≈ 3.17 tons.
- Because the density assumption changes the answer by roughly 10%, ask your supplier for the specific product's density if you need a precise order quantity.
Step 4 — add waste and compaction allowance
Add 5-10% for spillage, uneven subgrade and settling. Compacted base layers can lose 15-20% of loose volume once rolled, so order toward the higher end when compaction is specified in a plan.
Typical gravel types and uses
Common gravel products and typical use
| Product | Typical size | Common use |
|---|---|---|
| Crusher run | Mixed fines to 3/4 in | Compacted driveway base |
| Pea gravel | 3/8 in rounded | Paths, drainage, decorative beds |
| 3/4 in crushed stone | 3/4 in angular | Driveway top layer, drainage |
| River rock | 1-3 in rounded | Decorative landscaping |
Common mistakes
- Forgetting to convert depth from inches to feet before multiplying, which inflates the result by 12x.
- Using a single national density figure instead of the supplier's actual product density.
- Not accounting for compaction loss when a base layer will be rolled or plate-compacted.
- Ignoring an edging or border that changes the effective area to be filled.
Practical considerations
Bulk gravel is usually cheaper per ton than bagged gravel, but delivery minimums and access for a dump truck matter for small residential jobs. For areas under roughly 1-2 cubic yards, bagged gravel from a hardware store is often more practical despite the higher per-ton price.
Second example: a full driveway build-up
Larger projects often layer two depths — a compacted base and a top dressing — which need to be calculated and ordered separately.
- Driveway: 40 ft long x 12 ft wide.
- Base layer: 6 inches (0.5 ft) of crusher run. Volume: 40 x 12 x 0.5 = 240 cubic feet = 8.89 cubic yards.
- Top layer: 3 inches (0.25 ft) of 3/4 in crushed stone. Volume: 40 x 12 x 0.25 = 120 cubic feet = 4.44 cubic yards.
- At 105 lb/ft³, the base layer weighs roughly 240 x 105 / 2,000 ≈ 12.6 tons, and the top layer roughly 120 x 105 / 2,000 ≈ 6.3 tons.
- Add 10% for compaction and waste on the base layer specifically, since it will be compacted after placement: 12.6 x 1.10 ≈ 13.9 tons.
How far a ton of gravel goes at common depths
Approximate coverage per ton at 105 lb/ft³ density
| Depth | Approx. coverage per ton |
|---|---|
| 2 in | ≈ 115 sq ft |
| 3 in | ≈ 77 sq ft |
| 4 in | ≈ 58 sq ft |
| 6 in | ≈ 38 sq ft |
Frequently asked questions
How many tons of gravel are in a cubic yard?
It depends on density, but a common estimate is roughly 1.3-1.5 tons per cubic yard for typical crushed stone. Because gravel density varies by material, confirm the specific product's weight-per-yard with your supplier for an exact figure.
How much extra gravel should I order for waste?
5-10% covers typical spillage and an uneven subgrade for most projects. For a base layer that will be compacted, order toward the higher end or add a separate compaction allowance, since compacted material occupies less volume than loose material.
What depth of gravel do I need for a driveway?
A full driveway build typically uses a compacted base of several inches plus a top layer of 3-4 inches, for a combined depth commonly in the 8-12 inch range depending on soil conditions and expected vehicle loads.
How much area does one ton of gravel cover?
It depends entirely on depth and density. At a typical crushed-stone density and a 3-inch depth, one ton covers roughly 75-80 sq ft; the same ton spread at 6 inches covers about half that area, since coverage is inversely proportional to depth.
Can I use the same formula for sand or mulch?
The volume step (length x width x depth) is identical for any bulk material. Only the density used to convert volume to weight changes — sand is considerably denser than gravel, and mulch is much lighter, so use the specific product's density rather than reusing a gravel figure.
How do I measure an irregularly shaped area for gravel?
Split the area into rectangles and triangles, calculate each section's area separately, add them together, then multiply the combined area by the depth to get total volume, the same approach used for irregular rooms in flooring calculations.
Sources and references
- USDA NRCS — Gradation and aggregate specifications — Reference material on aggregate gradation and compacted density assumptions.
- Federal Highway Administration — Aggregate base course guidance — Base-course thickness and compaction practice used for driveway depths.
- NIST Handbook 44 — Weights and measures — Standard short-ton and volume definitions behind the tonnage conversion.