Gravel Calculator

How much gravel do you actually need?

The calculation itself is simple arithmetic, but three things trip people up often enough that they are worth spelling out. The first is unit mixing: your area is in square feet and your depth is in inches, so the depth has to be converted to feet before anything is multiplied. Skipping that conversion produces an answer twelve times too large, and it is by far the most common error in manual gravel calculations.

The second is the difference between volume and weight. Suppliers sell gravel by the ton, but every plan and every calculator works in cubic yards. Converting between them requires the density of the specific stone you are buying — and densities vary from about 1.35 tons per cubic yard for rounded pea gravel up to 1.5 for crusher run. Using a single generic figure can put you out by 10% on a large order, which is most of a truck load.

The third is compaction. Gravel settles. Angular stone locks together and loses volume as it is compacted, and some material always works down into the subgrade on the first pass. Ordering the exact finished volume reliably leaves you short. A 10% allowance is standard practice, and 15% is sensible over soft or wet ground.

Choosing the right depth

Depth is the variable that most affects your total, and it is set by load rather than appearance. A decorative bed nobody walks on needs two inches. A patio surface needs two inches over a compacted base. A new driveway needs eight to twelve inches built in layers. Doubling the depth doubles the cost, so this is the number worth getting right before you order rather than after.

If you are unsure, the gravel depth calculator picks the depth from your application, and will also tell you how far the stone you already have will actually spread.

Bulk or bagged?

A cubic yard is 27 cubic feet, which is 54 standard half-cubic-foot bags. At typical retail prices that is well over $300 per cubic yard against roughly $45 to $95 delivered in bulk. Bags only make sense below about half a cubic yard, where a flat delivery fee would dominate the bill. The bagged gravel calculator finds the crossover point for your specific job.

Ordering

Delivery is charged per truck load, not per ton, so the size of your order matters more than most people expect. Ordering thirteen tons when a tandem dump carries twelve means paying two full haul fees. Round your order to fill loads where you can, and check it against the delivery calculator before you call the quarry.

Round the final figure up to whatever increment your supplier sells in — usually half a ton or a full yard. Running short mid-job costs another delivery fee, which is almost always more than the extra material would have cost.