Gravel Calculator: Estimate Tons Needed

A gravel calculator estimates the weight of gravel in tons (or tonnes) based on the volume you plan to fill. You enter the length, width, and depth of the area, and the calculator returns the cubic yards and the corresponding tons, using the density of the gravel you select. This lets you order the right amount for a driveway, path, or base layer without guesswork.

Formula

The calculator uses the standard formula for bulk material volume and weight:

Tons = (Length × Width × Depth) ÷ 27 × Density

Where:

• Length (ft) – the longer dimension of the area.
• Width (ft) – the shorter dimension of the area.
• Depth (in) – how thick you want the gravel layer, converted to feet by dividing by 12.
• 27 – the number of cubic feet in one cubic yard (3 ft × 3 ft × 3 ft).
• Density (tons per cubic yard) – varies by gravel type, typically 1.3 to 1.5 tons/yd³.

The result is in short tons (US tons, 2,000 lb). For metric tonnes (1,000 kg), multiply the result by 0.907.

Worked Example

Using the default values: length = 20 ft, width = 10 ft, depth = 4 in, material = pea gravel (density 1.4 tons/yd³).

1. Convert depth to feet: 4 in ÷ 12 = 0.333 ft.
2. Calculate volume in cubic feet: 20 × 10 × 0.333 = 66.6 ft³.
3. Convert to cubic yards: 66.6 ÷ 27 = 2.47 yd³.
4. Multiply by density: 2.47 × 1.4 = 3.46 tons.

The calculator shows 3.46 tons and 2.47 cubic yards. That matches the default output.

Why Gravel Density Varies

Gravel is not a single material. The density depends on the rock type, particle size, and moisture content. A cubic yard of dry pea gravel weighs about 1.4 tons, while crushed stone with fines can reach 1.5 tons or more. River rock, being round and uniform, packs less tightly and stays near 1.3 tons per cubic yard. If you are ordering from a supplier, ask for the exact density they use; many quote in pounds per cubic foot (e.g., 105 lb/ft³ = 1.42 tons/yd³). Using an average when the actual material is heavier can leave you short by 5–10%.

How to Measure Your Area

Accurate measurements matter more than precision in the formula. For a rectangular area, measure length and width in feet, and decide the depth in inches based on the project:

• Walkway or path: 2–3 inches.
• Driveway (with proper base): 4–6 inches for passenger cars.
• Base layer under pavers: 4–6 inches, compacted.
• French drain or trench: 8–12 inches, depending on pipe diameter.

For irregular shapes, break the area into rectangles and triangles, calculate each separately, then sum the tons. For a circular garden bed, use the formula π × radius² for area, then multiply by depth and density.

Common Mistakes and Misconceptions

The biggest error is mixing units – entering depth in inches but using a formula that expects feet, or entering length in yards but width in feet. Always convert everything to feet first. Another frequent mistake is forgetting that gravel compacts. Freshly dumped gravel settles by about 10–15% when rolled or driven on. If you order exactly the calculated volume, you may end up slightly low after compaction. Order 10% extra to account for settling and for irregular ground. A third misconception is that a cubic yard equals a ton – it does not. A cubic yard of gravel weighs between 1.3 and 1.5 tons, so never use a 1:1 ratio.

How to Order Gravel

Suppliers sell gravel by the cubic yard or by the ton. If they quote per cubic yard, you can use the cubic yard output from the calculator directly. If they quote per ton, use the tons output. When ordering, specify the material type (e.g., #57 crushed stone, pea gravel, bank run gravel) and the depth you plan to spread. Ask about delivery fees and minimum order quantities – many suppliers have a 1-ton minimum, and delivery can cost more than the gravel itself for small loads. For a project under 2 tons, consider buying in 50 lb bags from a home center, but be aware that 1 ton equals 40 bags, which is heavy work.

Cost Considerations

While prices vary by region and supplier, gravel typically costs $15–$30 per ton for bulk material, with decorative stone like river rock at the higher end. Delivery adds $50–$150 depending on distance. The calculator helps you avoid over-ordering, but it cannot account for local price fluctuations. A 20×10 ft driveway at 4 inches deep (about 3.5 tons) might cost $50–$100 for the gravel alone, plus delivery. Compare that to bagged gravel, which can cost three to four times more per ton. For large projects, always get quotes from at least two local suppliers.

Safety and Spreading Tips

Gravel is heavy – a full pickup truck bed holds about 1.5 tons, which can exceed the payload rating of many half-ton trucks. Check your vehicle’s payload capacity before loading. When spreading gravel, wear gloves and eye protection, especially with crushed stone that has sharp edges. Use a rake and a level to distribute evenly, and compact with a plate compactor for driveways. Avoid spreading gravel on a slope steeper than 10% without a retaining edge, as it will wash away in rain. For walkways, lay landscape fabric underneath to prevent weeds from growing through.

Frequently Asked Questions

How many tons of gravel do I need for a 100 ft driveway?
For a 100 ft long, 10 ft wide driveway at 4 inches deep, the volume is 100 × 10 × 0.333 = 333 ft³ = 12.3 yd³. At 1.4 tons/yd³, that is about 17.3 tons. Most suppliers will round up to 18 tons.

What is the difference between a ton and a cubic yard?
A ton is a unit of weight (2,000 lb). A cubic yard is a unit of volume (27 ft³). Gravel density links them: 1 cubic yard weighs about 1.4 tons, so 1 ton is roughly 0.7 cubic yards. Always use the density to convert, not a fixed ratio.

Should I order extra gravel?
Yes, order 10% more than the calculated amount. This accounts for compaction, uneven ground, and spillage during spreading. For a 3-ton order, that means adding about 0.3 tons.

Can I use this calculator for sand or soil?
No, sand and soil have different densities. Sand is about 1.1–1.3 tons per cubic yard, and topsoil is 0.9–1.1 tons per cubic yard. Use a separate calculator or adjust the density manually if your supplier gives you the exact value.

What depth should I use for a gravel patio?
For a patio that will have furniture and foot traffic, use 3–4 inches of gravel over compacted soil. If you plan to put pavers on top, add a 1-inch layer of sand over the gravel. The calculator’s default of 4 inches works well.

How do I measure an L-shaped area?
Split it into two rectangles, calculate each separately, and add the tons together. For example, a 10×10 ft section and a 5×10 ft section at 4 inches deep would be (10×10×0.333/27 + 5×10×0.333/27) × 1.4 = 2.59 tons.

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in l | Length | ft | 20 | 0
in w | Width | ft | 10 | 0
in d | Depth | in | 4 | 0
sel mat | Material | Pea Gravel=1.4, Crushed Stone=1.35, River Rock=1.3, Limestone=1.5
out tons | Estimated Tons | tons | (l * w * (d / 12) / 27) * mat | 2
out cubic_yds | Cubic Yards | yd³ | l * w * (d / 12) / 27 | 2