YardCompute / Project Guides / Gravel Depth and Coverage
How to Calculate Gravel Depth and Coverage
Gravel quantity depends on the area you need to cover and the depth of the gravel layer. The basic calculation is simple, but mixing inches and feet or using an inconsistent depth can produce a wrong order quantity.
1. Measure the area
For a rectangular area, measure the length and width in feet. Multiply them to get square feet.
Area = length × width
For example, a 20 ft × 10 ft area has 200 square feet.
2. Choose the gravel depth
Use the depth specified for your project. Measure the planned layer thickness rather than guessing from the amount of material you intend to buy.
If depth is given in inches, convert it to feet by dividing by 12. For example, 3 inches is 0.25 ft and 4 inches is about 0.333 ft.
3. Calculate gravel volume
Multiply the area by the depth in feet:
Volume = area × depth
Example: 200 sq ft at 3 inches deep:
200 × (3 ÷ 12) = 50 cubic feet
4. Add a planning allowance
Depending on the project, an allowance can account for minor measurement differences, spreading, settlement, compaction, and waste. If you use a 10% planning allowance, multiply the base volume by 1.10.
50 × 1.10 = 55 cubic feet
The appropriate allowance varies by project, so treat it as a planning input rather than a universal rule.
5. Convert volume when buying by weight
Suppliers may sell gravel by tons rather than cubic feet. To estimate weight, use the bulk density supplied for the material.
Tons = cubic feet × density in lb/cu ft ÷ 2,000
For example, 55 cubic feet at 105 lb/cu ft is about 2.89 tons. Actual density varies with material type, grading, moisture, and supplier.
Irregular areas
For an L-shaped, curved, or otherwise irregular area, divide the project into simple sections that can be measured separately. Calculate each section and add the volumes together. Keep the planned depth consistent unless different areas intentionally use different depths.
Why depth changes the quantity so much
Area tells you how much surface is covered, while depth determines how much material is stacked over that surface. Doubling the depth doubles the calculated volume when the area stays the same. That is why a small depth error can create a meaningful difference in the material estimate.
Common mistakes
- Using inches as though they were feet.
- Using one depth for areas that actually have different layer thicknesses.
- Confusing square feet with cubic feet.
- Assuming every gravel material has the same density.
- Treating a planning allowance as a guaranteed waste percentage.
Use the Gravel Calculator
For a faster estimate, use the YardCompute Gravel Calculator. For driveway-specific estimates, use the Driveway Gravel Calculator and see the driveway gravel calculation guide.
FAQ
How do I convert gravel depth from inches to feet?
Divide the depth in inches by 12. For example, 4 inches equals 0.3333 feet.
How much gravel is needed for a 200 square foot area?
The amount depends on depth. At 3 inches, the base volume is 50 cubic feet before any planning allowance.
Does deeper gravel always mean more material?
Yes. With the same area, volume increases in direct proportion to depth.
Should I use the same gravel density for every project?
No. Density varies by aggregate type and supplier. Use supplier information when available.
How should I calculate an irregular area?
Break it into measurable sections, calculate each section separately, then add the volumes.
Related calculators
Gravel Calculator · Driveway Gravel Calculator · Mulch Calculator
Planning estimate: Estimates are for planning purposes only. Actual material requirements may vary based on site conditions, material specifications, installation methods, waste, and local requirements. Always verify quantities with your supplier or qualified professional before purchasing materials.