This gravel calculator works out the volume of gravel you need in cubic yards and cubic feet, plus an estimate of the weight in tons. You enter the length and width of the area in feet, the depth you want in inches, and the calculator returns the volume and a tonnage estimate based on the typical density of gravel. It is designed for driveways, walkways, and garden beds where you need to order the right amount of material.
Formula
The volume of gravel is calculated using the formula for the volume of a rectangular prism:
Volume (ft³) = Length (ft) × Width (ft) × Depth (in) ÷ 12
To convert cubic feet to cubic yards, divide by 27 (since 1 yard = 3 feet, so 1 yd³ = 27 ft³). Combining the two steps gives:
Volume (yd³) = (L × W × D) ÷ 324
Where:
- L = length of the area in feet (ft)
- W = width of the area in feet (ft)
- D = depth of gravel in inches (in) – note that you enter inches, so we convert to feet by dividing by 12
The divisor 324 comes from 27 (ft³ per yd³) × 12 (inches per foot).
Worked Example
Using the default values: length = 40 ft, width = 25 ft, depth = 3 in.
- Convert depth to feet: 3 in ÷ 12 = 0.25 ft
- Calculate volume in cubic feet: 40 × 25 × 0.25 = 250 ft³
- Convert to cubic yards: 250 ÷ 27 = 9.26 yd³
The calculator shows 9.26 yd³ and 250.0 ft³, matching the manual calculation.
To estimate weight in tons, multiply the cubic yards by the density of gravel. A typical loose gravel density is about 1.4 tons per cubic yard (or 2,800 lb/yd³). So for 9.26 yd³: 9.26 × 1.4 ≈ 13 tons. However, density varies with gravel type and moisture, so treat this as an estimate.
When to Use This Calculator
Use this gravel calculator whenever you need to order gravel for a project. Common situations include:
- Laying a new gravel driveway – typical depth is 4–6 inches for a vehicle surface.
- Creating a walkway or path – usually 2–3 inches deep.
- Filling a garden bed or French drain – depth depends on the purpose.
- Ordering gravel for a paver base – often 4–6 inches compacted.
The calculator works for any rectangular area. For irregular shapes, break the area into rectangles, calculate each, and add the volumes.
How to Choose the Right Gravel Type
Different projects need different gravel. The calculator gives volume, but you also need to pick the right material:
- Crushed stone (e.g., #57 or #67) – angular, compacts well, good for driveways and base layers.
- Pea gravel – round, smooth, comfortable to walk on, but shifts easily; best for paths and play areas.
- River rock – larger, decorative, doesn’t compact; used for landscaping and drainage.
- Decomposed granite – fines that pack hard; good for paths and patios.
For a driveway, crushed stone with angular edges interlocks and stays in place better than round gravel. For a walkway, pea gravel is gentler underfoot. Always confirm with your supplier that the gravel you choose is suitable for your project.
Common Mistakes and How to Avoid Them
Many people underestimate the amount of gravel needed. Here are the most frequent errors:
- Mixing units – entering depth in feet instead of inches, or length in yards instead of feet. Always double-check the units on the calculator.
- Forgetting compaction – gravel compacts when rolled or driven on. If you plan to compact, order about 10–15% extra to account for settling.
- Ignoring the subgrade – if the ground underneath is soft, you may need a thicker layer. The depth you enter should be the final compacted depth, not the loose depth.
- Rounding too early – rounding the volume to a whole number before converting can cause a significant error. Keep at least two decimal places until the final step.
Also, gravel is often sold by the cubic yard, but sometimes by the ton. If your supplier quotes by the ton, multiply cubic yards by the density (typically 1.3–1.7 tons per cubic yard) to get the weight.
Limits of the Formula
This calculator assumes a perfectly flat, rectangular area with uniform depth. Real-world projects have slopes, curves, and irregularities. The formula also does not account for:
- Compaction – gravel settles, so the actual amount needed may be higher.
- Waste and spillage – it’s wise to order 5–10% extra.
- Variations in gravel density – different types weigh differently; the tonnage estimate is approximate.
- Depth variations – if you need a thicker layer in some areas, calculate each section separately.
For large projects, always consult with your gravel supplier. They can provide specific density figures for the material you choose and help you adjust for compaction.
Frequently Asked Questions
How many cubic feet are in a ton of gravel?
A ton of gravel is roughly 20–22 cubic feet, depending on the density. Since 1 cubic yard = 27 cubic feet, a ton is about 0.74–0.81 cubic yards. For a typical gravel density of 1.4 tons per cubic yard, 1 ton = 1/1.4 ≈ 0.71 yd³, which is about 19.3 ft³. Always check with your supplier for the exact density.
How deep should gravel be for a driveway?
For a residential driveway, a compacted depth of 4–6 inches is standard. If the soil is soft or you have heavy vehicles, go with 6 inches. For a walkway, 2–3 inches is usually enough. The calculator lets you adjust the depth to see how volume changes.
What is the difference between gravel and crushed stone?
Gravel is naturally rounded rock, often found in riverbeds, while crushed stone is mechanically broken into angular pieces. Crushed stone compacts better and is preferred for driveways and bases. Gravel is more decorative and easier to walk on, but it shifts under weight.
How much does a cubic yard of gravel weigh?
A cubic yard of gravel typically weighs between 2,400 and 2,900 pounds (1.2 to 1.45 tons). The exact weight depends on the type and moisture content. For planning, use 2,800 lb/yd³ (1.4 tons/yd³) as a general estimate.
Should I order extra gravel?
Yes, it’s a good idea to order 5–10% more than the calculated volume. This accounts for compaction, spillage, and uneven ground. For a driveway that will be compacted, add 10–15% to the calculated amount.