Pea gravel calculator

How this is calculated

1. Shape areas are summed and multiplied by depth: volume = total area × depth (at depth d inches, cubic yards = square feet × d ÷ 324).
2. Tonnage = volume × conversion factor, shown as a range at 1.5–1.7 tons per cubic yard — the Wisconsin DOT statewide factor for the coarse sand / sand-and-gravel aggregate class, compacted in place. We could not find a pea-gravel-specific producer figure worth citing, so we show the class range and say so, rather than inventing precision.
3. Bags = ⌈volume ÷ bag size⌉, using the size printed on the bag.

Data used, with sources

Tons here means US short tons (2,000 lb).

Why the tonnage is a range

Pea gravel is sold both by the cubic yard and by the ton, and every quarry converts between the two with its own factor — stone type, moisture, and gradation all move the number. The cited figure here is the class conversion covering coarse sand and gravel, the same one the sand calculator uses, because no pea-gravel-specific producer figure was worth citing. Calculators that print a single tons-per-yard figure are hiding that spread, not resolving it. If your supplier sells by the ton, ask for their conversion; if you can order by volume, do — the cubic-yard figure above involves no conversion at all.

Choosing a depth

For beds and ground cover, extension guidance runs 2–4 inches: Utah State Extension puts inorganic mulch at 2–3 inches; Colorado State Extension uses 4 inches where weed suppression is the goal and notes a 3-inch gravel layer sharply improves water infiltration — with the explicit warning that more is not better. For stones to function as mulch at all, Colorado State advises keeping them under half an inch in diameter — which is what pea gravel is. Larger rounded stone is a different order entirely: the river rock calculator carries depths cited by particle size, and they run deeper.

Bags or bulk?

Pea gravel bags are small — commonly half a cubic foot — so a single cubic yard is 54 bags. That makes the break-even arrive fast: bags win for a stepping-stone joint, a planter topping, a fountain basin, or anywhere you must carry material through a house, and unlike mulch, unopened bags keep indefinitely for touch-ups. Beyond roughly half a yard, get a bulk quote: one dump of a supplier's loader replaces dozens of lifts, and bulk stone is dramatically cheaper per cubic foot. If the result above reads in whole cubic yards, you are shopping for a delivery, not a cart of bags.

Common mistakes

• Using pea gravel as a compacted base. Rounded, uniform stones roll instead of locking — the measured compaction figures in the cited engineering report are for graded sand-and-gravel mixes, which is exactly why this page deliberately applies no compaction factor. A patio or driveway base wants crushed stone with fines, not pea gravel.
• Skipping the edging. Colorado State Extension warns that mulch without a defined edge spreads off the bed onto lawns and sidewalks, creating a mowing or trip hazard — and pea gravel, being round, migrates worst of all. Contain it, or plan to sweep it forever.
• Assuming fabric underneath is settled practice. Extension guidance genuinely diverges: Utah State allows a permeable landscape fabric under inorganic mulch (about a five-year service life, never impermeable plastic sheeting), while Colorado State advises skipping fabric entirely — at the correct depth it adds nothing, weeds germinate on top and root through it, and it interferes with water and air exchange. Decide by how much soil contact and future replanting you want, not by habit.
• Piling it deeper than the cited range. Colorado State is blunt that more is not better: past about 4 inches you pay for stone that reduces air exchange to the soil instead of suppressing more weeds.
• Ignoring heat. Gravel mulch transfers more heat to the underlying soil than wood chips (Colorado State) — an advantage in cold winters, but next to buildings and tender plantings it can push heat where you don't want it and wake plants too early in spring.

Frequently asked

Sources

• Weight-Volume Relationships and Conversion Factors for Soils and Aggregates of Wisconsin (WHRP G22-05) — Wisconsin Department of Transportation / Wisconsin Highway Research Program, accessed Jul 31, 2026.
• Water-Wise Landscaping: Mulch — Utah State University Extension, accessed Jul 31, 2026.
• CMG GardenNotes #245: Mulching — Colorado State University Extension, accessed Jul 31, 2026.