How it's calculated
Gravel and crushed stone are measured by volume but usually sold by weight. The calculator finds the volume of the area at the depth you want, then multiplies by a density in tons per cubic yard to get the weight to order. It also shows how many bags that weight would fill, for small jobs bought at a store.
Density is the number that matters most, and it changes with the stone, its grading and how tightly it is packed. The built-in figures are the conversion factors the Wisconsin Department of Transportation uses to turn compacted, in-place base course from cubic yards into tons: 1.85 tons per cubic yard for dense-graded base aggregate Wisconsin DOT and 1.75 tons per cubic yard for select crushed material Wisconsin DOT. Because those are in-place figures, enter the depth you want after compaction. For loose decorative stone such as pea gravel or river rock, choose "My supplier's density" and enter the figure your quarry or supplier quotes.
The formula
- Area = length × width (square feet).
- Cubic yards = area × depth in inches ÷ 324 (27 cubic feet per cubic yard × 12 inches per foot), plus any extra allowance.
- Tons = cubic yards × density in tons per cubic yard. One short ton is 2,000 lb.
- Bags = pounds ÷ bag weight, rounded up. QUIKRETE All-Purpose Gravel comes in 50 lb (22.6 kg) bags QUIKRETE.
- Cost = tons × price per ton.
- Metric: cubic meters and metric tonnes use NIST's exact factors: 1 yd³ = 0.764554857984 m³ and 1 short ton = 907.18474 kg NIST.
Worked example
A 10 × 20 ft patio base, 4 inches deep after compaction, takes 2.47 cu yd of dense-graded crushed stone. At 1.85 tons per cubic yard that weighs 4.57 tons (9,136 lb), and costs $206 at an example $45 a ton.
Gravel needed: 2.47 cubic yards · 4.57 tons
Bought in 50 lb bags, the same base would take 183 bags, which is why larger jobs are usually delivered by the ton. A 3 × 30 ft garden path 3 inches deep in select crushed material weighs 1.46 tons.
Assumptions and limitations
- Density varies. The WisDOT factors are for compacted base aggregate meeting that state's specifications. Your supplier's material may be lighter or heavier, and wet stone weighs more than dry.
- Loose stone is different. Decorative stone that is spread loose and not compacted has a lower in-place density; use the supplier's figure. The FHWA-sponsored Gravel Roads Maintenance and Design Manual notes that ordinary compaction from traffic and rainfall makes most gravels shrink at least 20 percent South Dakota LTAP / FHWA, so loose and compacted volumes are not interchangeable.
- Compacted depth. Order for the finished, compacted depth. If you measure a loose layer before compacting, the weight from these factors will be too high.
- Bags are counted by weight. Bag volume isn't on the QUIKRETE data sheet, so bags are estimated from the weight at the chosen density.
- No delivery fee. Bulk prices usually exclude delivery.
- Prices are examples. Enter your own.
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