Pea Gravel Calculator

What pea gravel is good at

Pea gravel is rounded, water-worn stone at roughly three eighths of an inch. That rounding is the entire point: it is comfortable underfoot, kind to bare feet and paws, and it drains almost instantly. Around pools, in play areas, and in dog runs it outperforms every angular alternative.

What it is bad at

Rounded stone cannot interlock. It will not compact no matter how much you work it, it will not carry concentrated load, and it migrates continuously toward any edge that is not physically contained. On a driveway it ruts under tires and scatters. Under furniture legs it swallows them.

Neither of these is a defect — it is simply what rounded stone does. The failures happen when it is used where an angular stone belongs. The full comparison covers where each one wins.

Edging is mandatory

This is not a style preference. Without a hard perimeter, pea gravel spreads into the surrounding lawn and beds within a single season, and the area loses depth every year until soil shows through. Budget for edging around the entire perimeter — this calculator returns the linear footage you need.

The edging must be at least as deep as the gravel layer, ideally an inch or two deeper. A shallow strip simply gets undermined.

Put a base underneath

Pea gravel laid directly on soil sinks into it and mixes with dirt, and within two seasons you have a muddy, weedy surface rather than clean stone. For any patio or path, put down two to four inches of compacted crusher run over geotextile fabric first, then the pea gravel on top.

Playground depth is a safety spec

If you are surfacing under play equipment, the nine-inch depth this calculator applies is not a suggestion — it is the standard depth for pea gravel at fall heights up to about five feet. Check the standard that applies where you are, and confirm the equipment manufacturer's own requirement. Shallower fill does not attenuate a fall the way the specification assumes. The playground surfacing calculator adds the 6 ft use zone and works out the full 12 inch fill for pea gravel, sand or wood chips.