Granite Gravel Calculator: How Much Do You Need?

This granite gravel calculator works out the volume and weight of decomposed granite or crushed stone you need for a project. You enter the area’s length, width, and desired depth, and it returns the volume in cubic feet and cubic yards, plus the estimated weight in tons based on the material’s density. The result helps you order the right amount from a supplier without over- or under-buying.

Formula

The calculator uses two basic formulas:

• Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft)
• Weight (tons) = Volume (ft³) × Density (lb/ft³) ÷ 2000

Where:

• Length and Width are the dimensions of the area in feet (or convert meters to feet by multiplying by 3.28084).
• Depth is the desired thickness of the gravel layer in inches. It is converted to feet by dividing by 12.
• Density is the material’s weight per cubic foot. For granite gravel, typical values range from 130 to 150 lb/ft³ (2,080 to 2,400 kg/m³). The default of 145 lb/ft³ is a common average for crushed granite.

The result is given in cubic feet, cubic yards (volume in ft³ ÷ 27), and tons (weight in lb ÷ 2000).

Worked Example

Using the default values: length = 10 ft, width = 10 ft, depth = 3 in, density = 145 lb/ft³.

1. Convert depth to feet: 3 in ÷ 12 = 0.25 ft
2. Calculate volume in cubic feet: 10 × 10 × 0.25 = 25 ft³
3. Convert to cubic yards: 25 ÷ 27 = 0.926 yd³ (rounded to 0.9)
4. Calculate weight: 25 × 145 = 3,625 lb
5. Convert to tons: 3,625 ÷ 2000 = 1.8125 tons (rounded to 1.81)

So a 10×10 ft area with 3 inches of granite gravel needs about 0.9 cubic yards or 1.81 tons.

When to Use This Calculator

Use this calculator for any project that involves laying a gravel base or surface, such as:

• Building a patio or walkway with decomposed granite
• Creating a French drain or trench backfill
• Preparing a base for pavers or a shed
• Landscaping a garden path or driveway

The calculator works for any angular stone, not just granite—you can adjust the density to match the specific rock you plan to use. For example, limestone is often around 160 lb/ft³, while river rock (smooth pebbles) is lighter at about 100–120 lb/ft³.

How to Choose the Right Depth

The depth you need depends on the purpose:

• 2–3 inches: Light foot traffic, decorative ground cover, or under a small paver patio.
• 4–6 inches: Driveways or areas that will support vehicles. Heavier loads require more depth to prevent rutting.
• 6+ inches: Heavy equipment or commercial use. Always check local building codes for specific requirements.

If you are using granite gravel as a base for pavers, you might need an additional layer of finer stone (like stone dust) on top. That layer is usually 1–2 inches thick and should be calculated separately.

Common Mistakes and How to Avoid Them

• Mixing units: Always convert all measurements to the same unit before calculating. If you measure length in feet and depth in inches, you must divide depth by 12.
• Forgetting compaction: Granular materials compact when rolled or tamped. The volume you order should be about 10–15% more than the calculated volume to account for settling. For example, if the calculator says 1 cubic yard, order 1.1–1.15 cubic yards.
• Ignoring density variations: Different quarry sources have different densities. If you know the exact density from your supplier, use that instead of the default.
• Rounding too early: Round only at the final step. Rounding intermediate values can lead to significant errors, especially for large areas.

Understanding the Results

The volume in cubic yards is what most suppliers use to quote prices. The weight in tons is useful for estimating delivery costs, since trucks are often limited by weight. For example, a typical dump truck can carry 10–15 tons, while a smaller pickup might carry 1–2 tons.

If you are ordering by the bag (common for small projects), know that a 50-pound bag of decomposed granite covers about 2–3 square feet at 2 inches deep. That means a 10×10 ft area at 3 inches would need about 50 bags (since 3,625 lb ÷ 50 lb = 72.5, but with compaction you might need 80).

Limitations of the Formula

This calculator assumes a perfectly rectangular area with uniform depth. Real-world projects often have irregular shapes, slopes, or varying thickness. For non-rectangular areas, break the space into smaller rectangles and add the volumes together. For slopes, you might need extra material to account for erosion.

The density value is an average. Actual density varies with moisture content, particle size, and source. Wet gravel weighs more than dry gravel, so if you are ordering during rainy season, the weight might be higher than calculated. Always confirm with your supplier.

Frequently Asked Questions

How many square feet does a ton of granite gravel cover?

At a 3-inch depth, a ton of granite gravel (about 2,000 lb) covers roughly 55–60 square feet, depending on density. To get this, divide the weight by the density to find volume (2000 lb ÷ 145 lb/ft³ ≈ 13.8 ft³), then divide by the depth in feet (0.25 ft) to get area: 13.8 ÷ 0.25 ≈ 55 ft². For a 2-inch depth, it covers about 83 ft².

Should I order extra gravel for compaction?

Yes, it’s wise to add 10–15% to your calculated volume. Granular materials settle and compact when walked on or rolled, so the final surface will be lower than the initial loose depth. For example, if you need 1 cubic yard, order 1.1–1.15 cubic yards to avoid a second delivery.

What’s the difference between decomposed granite and crushed stone?

Decomposed granite (DG) is a naturally weathered granite that breaks down into small, angular particles. It compacts well and is often used for paths. Crushed stone is mechanically crushed rock, usually larger and more uniform. Both are calculated the same way, but DG typically has a density around 130–145 lb/ft³, while crushed granite can be up to 160 lb/ft³.

Can I use this calculator for other types of gravel?

Yes, just change the density to match the material. For example, pea gravel is about 105 lb/ft³, limestone is about 160 lb/ft³, and river rock is about 110 lb/ft³. The volume calculation stays the same; only the weight changes.

How do I measure an irregular area?

Divide the area into rectangles, calculate each rectangle’s volume, and add them together. For triangular or circular sections, use the appropriate area formulas (0.5 × base × height for triangles, Ï€ × r² for circles) and then multiply by depth. This calculator works best for rectangular spaces, but you can manually combine results.

Is it better to buy by the bag or by the bulk?

For small areas (under 50 ft²), bags are convenient but cost more per ton. For larger projects, bulk delivery is usually cheaper. A 50-lb bag costs roughly $3–$5, while bulk gravel is $20–$50 per ton, but delivery fees can add up. Use the calculator to find the total weight, then compare prices including delivery.

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in length | Length | ft | 10 | 0
in width | Width | ft | 10 | 0
in depth | Depth | in | 3 | 0
in density | Density | lb/ft³ | 145 | 0
out volume_ft | Volume | ft³ | length * width * (depth / 12) | 1
out volume_yd | Volume | yd³ | volume_ft / 27 | 1
out weight_tons | Weight | tons | (volume_ft * density) / 2000 | 2