Gravel Calculator

How it works

The area to be covered is treated as a rectangle, so the volume is length × width × depth. Length and width are in feet and depth is in inches, so the depth is divided by 12 first. That gives cubic feet; dividing by 27 converts to cubic yards, which is how bulk gravel is sold.

Suppliers often quote by weight rather than volume, so the volume is also converted to tons using a typical density for the material you chose: about 1.4 tons per cubic yard for gravel and pea gravel, and 1.5 for crushed stone. These are averages for dry, loose material; the figure for what your supplier actually delivers can differ, so treat the tons as a guide and the cubic yards as the firmer number.

For small jobs the volume is also given as 0.5 cu ft bags, the usual retail size, rounded up to whole bags. Once the count runs into the dozens, bulk delivery is almost always cheaper.

Formula

cubic feet  = length × width × (depth ÷ 12)
cubic yards = cubic feet ÷ 27
tons        = cubic yards × density
bags        = ⌈ cubic feet ÷ 0.5 ⌉
density: gravel ≈ 1.4, crushed stone ≈ 1.5, pea gravel ≈ 1.4 tons per cu yd

Example

A 20 ft × 10 ft driveway topped with 3 in of gravel needs 20 × 10 × 3⁄12 = 50 cu ft, which is 50 ÷ 27 = 1.85 cu yd. At about 1.4 tons per cubic yard that is roughly 2.59 tons.

In 0.5 cu ft bags it would be 100 bags, which is why bulk delivery is the usual choice at this size. Choosing crushed stone at 1.5 tons per cubic yard instead raises the weight to about 2.78 tons; the volume and bag count do not change.

Assumptions and limitations

• The area is a rectangle covered to a uniform depth. Split an irregular area into rectangles and add the results.
• Densities are typical supplier figures for dry, loose material and are approximate. Wet material, the amount of fines and the type of stone all change the weight. Ask the supplier for the density of what they will deliver.
• Gravel settles and compacts after it is laid. If the final compacted depth matters, for example under a slab or paver base, allow extra.
• No waste allowance is applied. Add 5–10% if the sub-grade is uneven or you want some spare.
• Bulk suppliers sell by the cubic yard or the ton, often with a minimum load.

Frequently asked questions