Volume equals length times width times depth in feet. Dividing by 27 converts cubic feet to cubic yards. Multiplying cubic yards by the material density (tons per cubic yard) gives the weight in tons to order.
Pea gravel and crushed stone are often compared, but they serve fundamentally different roles. Pea gravel is naturally smooth and rounded from water erosion, typically 3/8 inch diameter. It looks attractive, is comfortable underfoot and on bare paws, and drains well. But it will not compact. Under vehicle tires it forms ruts, throws stones, and migrates away from the surface. For any area that supports vehicle traffic, angular crushed stone (like #57 or #21A) is the right choice because the angular edges lock together under compaction.
Lava rock, the lightest material in the calculator at 0.8 tons per cubic yard, is a popular landscaping choice for desert-style plantings and fire pit surrounds because it is non-combustible and holds heat. Decomposed granite sits at 1.5 tons per yard and is denser than pea gravel, making it semi-compactable and useful for patios and paths that need a more stable surface than loose gravel. If your project also involves leveling or drainage work around the gravel area, a dirt fill estimate helps you calculate both materials in one planning session.
The depth you lay pea gravel to matters both for function and longevity. For garden paths and patios, 2 to 3 inches is the standard: less than 2 inches is patchy, displaces under foot pressure, and leaves visible gaps in the weed barrier. Dog runs need 3 to 4 inches, because dogs dig and move material around more aggressively than foot traffic does. Fire pit surrounds typically use 2 to 3 inches of a non-combustible material like pea gravel or lava rock within the perimeter. Drainage applications, around French drains and downspout outlets, call for 4 to 6 inches of open-graded gravel that allows water to infiltrate without clogging.
Always install landscape fabric before adding gravel to any bed or path. Without a barrier, weeds push through within one growing season and are nearly impossible to remove without displacing the surface. Landscape edging sunk 2 inches into the soil around the perimeter keeps pea gravel from migrating into adjacent lawns and beds. For drainage channel projects that also involve sand bedding around pipe, running a sand calculation alongside your gravel order ensures you have both materials before the excavation is open.