Pea gravel calculator: how much pea gravel do I need? (yards, tons and bags)

Pea gravel is the easiest stone to buy too much or too little of. It's laid shallower than driveway stone, it doesn't compact, and it's sold three different ways: by the ton at a quarry, by the cubic yard at a landscape yard and by the bag at a home center. This guide gives you the pea gravel formula, a coverage chart by depth, the number of bags for common projects, and a free calculator that does all of it on your phone.

Short answer: cubic yards = length × width × depth in inches ÷ 324. Multiply by about 1.35 tons per cubic yard for tons, or by 54 for 0.5 cu ft bags. A 16 × 12 ft patio at 3 inches takes about 1.8 cubic yards: roughly 2.4 tons, or 96 bags.

How deep should pea gravel be?

Depth is the number that decides everything else, and it depends on what the gravel is for:

• Garden beds and ground cover: 2 inches.
• Walkways and paths: 2 to 2.5 inches. Deeper than 3 inches and it feels like walking on a beach.
• Patios and seating areas: 3 inches, over a compacted base.
• Dog runs: 3 inches, so it can be raked and topped up.
• Under playground equipment: 9 inches. That's a safety depth for falls, not a look; check your local playground standard.

Patios and paths also need a base: 2 to 4 inches of compacted crusher run over landscape fabric. Pea gravel is rounded, so laid straight on soil it sinks and mixes with the dirt. Count the base separately: it compacts, so order about 15 to 25% more of it than the raw volume.

The pea gravel formula, step by step

1. Square feet = length × width (in feet). For a circle, 3.14 × radius × radius.
2. Cubic feet = square feet × depth in inches ÷ 12.
3. Cubic yards = cubic feet ÷ 27.
4. Tons = cubic yards × 1.35. Pea gravel weighs about 2,700 lb per cubic yard, or 100 lb per cubic foot.
5. Bags = cubic feet ÷ 0.5 for the common 0.5 cu ft (about 50 lb) bag.
6. Add 5 to 10% for an uneven subgrade and for what gets kicked out over the first season.

Densities vary by quarry and by how wet the stone is. Ask your supplier for their figure; most will tell you how many tons are in a cubic yard of their pea gravel.

Pea gravel coverage chart

How much ground one cubic yard (about 1.35 tons) covers at each depth:

Worked examples

Before waste. Round up to whatever your supplier sells: many sell bulk stone in half-yard or half-ton steps.

Bags or bulk?

Bags are convenient for a bed or a short path. Past about one cubic yard (54 bags), bulk is almost always cheaper and saves you lifting more than a ton of stone into a car. Bulk pea gravel typically runs about $35 to $70 per ton before delivery; a delivery fee often costs more than the stone on a small order, so compare one delivered price with the bag total. The 16 × 12 ft patio above is about $85 to $170 of stone in bulk.

Mistakes that cost a second trip

• Forgetting edging. Rounded stone migrates. Steel, aluminum, plastic or timber edging around the whole perimeter keeps it out of the lawn.
• Going too deep on a walking surface. 4 inches of pea gravel is hard to walk on and to push a wheelbarrow through.
• Using the crushed-stone weight. Calculators built for #57 or crusher run use a different density and add compaction pea gravel doesn't need.
• Skipping the base on a patio. Chairs sink in pea gravel laid straight on soil.

Use the calculator

The free Gravel & Stone Calculator for Android has a pea gravel mode with the depth for each use already set, and gives cubic yards, tons, bags, edging length and a cost range together. It works offline. In a browser, use the pea gravel calculator at smartgravelcalculator.com. On iPhone, a gravel calculator is part of Roofing Calculator & Estimator from version 1.7.

Choosing between pea gravel and crushed stone? See pea gravel vs crushed stone. For a driveway, read how many tons of gravel do I need, and for what to look for in an app, the gravel calculator app guide.