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Gravel Calculator
Enter the area and the depth you want when it is finished and rolled. The answer is what to order, not what fits in the hole.
The formula
finished volume = length × width × depth ÷ 12 ÷ 27
pounds = finished volume × compacted density × (1 + waste ÷ 100)
tons = pounds ÷ 2000
loose volume delivered = pounds ÷ loose density
Worked example
A 20 ft × 10 ft parking pad, 4 in finished, crushed surfacing
- 20 × 10 × (4 ÷ 12) = 66.67 ft³ = 2.47 yd³ finished
- 2.47 × 3,700 = 9,136 lb, + 10% stockpile waste = 10,049 lb
- 10,049 ÷ 2,000 = 5.02 tons to order
- 10,049 ÷ 2,850 = 3.53 yd³ arriving loose — 43% more than the hole
Where this goes wrong
Ordering the volume of the hole instead of the weight of the road
Gravel is sold by the ton and laid to a depth, and those two are separated by compaction. WSDOT publishes 2,850 lb for a cubic yard of crushed surfacing in the truck and 3,700 lb for the same material rolled into the road — a 30% gap. Multiply the hole by the loose figure and a 2.47 yd³ pad gets 3.52 tons instead of 4.57, which is roughly an inch short once it is rolled. The volume you dig is not the volume that turns up.
Questions
- How many tons of gravel are in a cubic yard?
- Between about 1.4 and 1.95, depending on the material and whether it is loose or compacted. WSDOT publishes 1.43 tons per cubic yard for crushed surfacing in the truck and 1.85 for the same material rolled into place, and 1.95 for ballast. A single answer to this question is always leaving something out.
- Why does this ask for two densities?
- Because the material has two, and the difference is the whole calculation. One converts the depth you want into a weight to buy; the other tells you how much room the load needs when it is tipped. Your supplier can give you both for what they actually sell — the defaults here are a highway department’s figures for highway material.
- How deep should a gravel driveway be?
- Depths depend on the subgrade, the traffic and local practice, and this page will not invent a rule for you. What it will say is that the depth you enter should be the finished, compacted depth, because that is what the weight is calculated from.
- Do these weights change when it rains?
- Yes, and WSDOT says so explicitly: the published figures are dry weights and require correction for water content. Aggregate delivered after rain carries water you are paying for by the ton, which is one reason suppliers and buyers argue about scale tickets.