How Much Gravel Do I Need? Gravel Calculator + Coverage Charts

How Much Gravel Do I Need?

Multiply length × width (ft) × depth (in.) ÷ 324 to get cubic yards, then multiply by 1.4–1.5 for tons. Use the free gravel calculator below for instant results, or follow the step-by-step formula further down. This is one of the guides on OnSiteCalculator.

Gravel Calculator Formula (Cubic Yards & Tons)

The contractor-tested gravel formula used on every job site:

Cubic yards = (Length ft × Width ft × Depth in.) ÷ 324

Tons = Cubic yards × Density (t/yd³)

The number 324 comes from 27 ft³/yd³ × 12 in./ft. It converts directly from inches-deep to cubic yards without an intermediate step.

Step-by-Step Example

Calculate gravel for a 20 × 30 ft patio at 3 inches deep using pea gravel (1.4 t/yd³):

1. Cubic yards: (20 × 30 × 3) ÷ 324 = 1,800 ÷ 324 = 5.56 yd³
2. Tons: 5.56 × 1.4 = 7.8 tons
3. Add 10% waste: 5.56 × 1.1 = 6.1 yd³ / 8.6 tons to order

For odd-shaped areas, split the project into rectangles, calculate each separately, and add the totals. The gravel calculator handles irregular layouts and includes optional waste and compaction fields.

Gravel Coverage Per Cubic Yard

One cubic yard covers different areas depending on how deep you spread it:

Coverage values are approximate. Actual coverage varies with spreading technique, settling, and material shape.

For coverage broken out by ton (how many square feet one ton covers at each depth), see the gravel coverage per ton guide.

Gravel Type Reference: Density, Coverage, and Best Use

Different gravel types have different densities. Using the wrong density when converting cubic yards to tons can throw off your order by 10–15%. For pre-calculated conversion charts and a full density table, see the cubic yards to tons gravel guide.

Tip: Always confirm the density with your supplier. Moisture content and particle size vary by region and season.

#57 Gravel vs Pea Gravel

#57 gravel (angular, ¾–1 in.) locks together when compacted, making it the right choice for driveways, French drain fill, and structural bases. It does not shift under vehicle loads.

Pea gravel (smooth, ⅜ in.) does not compact well and shifts underfoot, which makes it comfortable for bare-foot paths and playgrounds but a poor choice for vehicle traffic. It is easier to spread and gives a cleaner decorative look.

Both cost about the same per ton and share a density of roughly 1.4 t/yd³, so the formula is identical — only the use case differs.

Driveway Gravel Calculator

Residential driveways require more depth than landscaping paths. Follow these guidelines:

• 4 inches: Minimum for light vehicle traffic (passenger cars, occasional truck)
• 6 inches: Standard for everyday vehicle use
• 8 inches or more: Heavy equipment, commercial vehicles

For a two-layer driveway, calculate each layer separately. A typical setup is 4 in. of compacted #3 base stone topped with 2 in. of #57 or pea gravel finish.

Worked Example: 12 × 60 ft Driveway

Add 10% waste and compaction allowance: 14.7 yd³ / 21.7 tons to order.

If you are adding a concrete slab over a compacted gravel sub-base, the concrete slab calculator estimates the concrete volume on top.

French Drain Gravel Calculator

A French drain uses a perforated pipe surrounded by washed angular gravel (typically #57 or pea gravel) to redirect subsurface water.

Formula: Trench volume (ft³) = Length × Width × Depth (all in feet)

For the gravel volume, subtract the pipe volume (typically 10–15% of total trench volume for 4-in. pipe) and convert to cubic yards:

Gravel yd³ = (Trench ft³ × 0.87) ÷ 27

Example: 50 ft French Drain

Trench: 50 ft long × 1 ft wide × 1.5 ft deep = 75 ft³ Subtract 13% for pipe: 75 × 0.87 = 65.25 ft³ Convert to cubic yards: 65.25 ÷ 27 = 2.4 yd³ of gravel Tons (pea gravel, 1.4 t/yd³): 2.4 × 1.4 = 3.4 tons

Add 15% for settling in drainage applications: 2.8 yd³ / 3.9 tons to order.

Use washed gravel (no fines) for French drains. Fines clog the perforated pipe over time.

Waste and Compaction Allowances

Always order more than the raw calculation shows. Gravel is lost to:

• Spreading: Some material is thrown wide during delivery and hand-spreading
• Settling: Gravel compacts 5–10% under load after installation
• Low spots: Uneven sub-grade requires extra fill
• Delivery loss: Material remains in the truck bed or spills during delivery

To apply: Multiply your base cubic yards by (1 + waste factor). For 5.5 yd³ with 10% waste: 5.5 × 1.10 = 6.05 yd³ to order.

The gravel calculator has dedicated waste and compaction fields that apply these allowances automatically.

Common Ordering Mistakes

Measuring depth in feet instead of inches. If your planned depth is 4 inches and you enter 4 feet into a formula, your estimate will be 12× too large. Always convert: 4 in. ÷ 12 = 0.333 ft.

Skipping compaction. Gravel compacts significantly under vehicle traffic. A freshly spread 4-inch layer may compact to 3.5 inches after the first season. Order with a 10% compaction buffer on driveways.

Ordering by the wrong unit. Some suppliers sell by the cubic yard, others by the ton. Confirm with your supplier and use the matching output from the calculator.

Using bulk density instead of loose density. Gravel density values used in estimating (1.4–1.5 t/yd³) reflect loose, uncompacted material in the truck — the same state you order it in. Do not use compacted density for ordering.

Related Tools

• Gravel Calculator — Enter area, depth, gravel type, waste, and compaction to get cubic yards and tons with optional cost estimate.
• Cubic Yards to Tons Gravel Guide — Pre-calculated conversion charts in both directions and density values for every common gravel type.
• Gravel Coverage Per Ton Guide — Square footage coverage tables for pea gravel, crushed stone, river rock, and more at every common depth.
• Concrete Slab Calculator — Estimate concrete volume for slabs and driveways poured over a compacted gravel sub-base.
• Mulch Calculator — Calculate cubic yards and bags of mulch for landscape beds adjacent to your gravel project.