Gravel is not one material. Pea gravel, crushed stone, river rock, and decomposed granite look different, feel different underfoot, move differently, and need different depths. This guide explains each type, how depth changes the amount you need, and how to check a quantity before you order.
Summary: key takeaways
- Pea gravel is small, rounded stone that is comfortable to walk on but can scatter and migrate.
- Crushed stone is angular, locks together, and is a steadier choice for paths and driveways.
- River rock is smooth, rounded, and mainly decorative; it does not lock together like crushed stone.
- Decomposed granite is finely crushed granite that can pack into a firmer surface, but it needs edging and care with drainage.
- For the same area and depth, tonnage differs by type, because the densities stated on the linked calculators differ.
The four types
Pea gravel is made of small, rounded stones. It drains well and is easy to walk on, but it shifts underfoot and can be kicked onto lawns and paths, so edging helps. Crushed stone is angular, so the pieces interlock and form a more stable surface; that is why it is commonly used where people walk or vehicles drive. River rock is smooth and rounded by water, and is used mainly as a decorative cover, around plants, and in dry creek features; it rolls more easily than crushed stone. Decomposed granite is granite broken down into small particles and fines, which can compact into a relatively firm, natural-looking surface for paths and patios, but it can wash or track in heavy rain if drainage and edging are poor.
Density and depth comparison
The table below is on a single stated basis so the types can be compared: a 10-foot by 10-foot area (100 square feet) at a depth of 3 inches. The densities are the ones stated on the linked calculators; decomposed granite is not given a density on those calculators, so no tonnage is calculated for it here.
| Gravel type | Density stated on the linked calculator (tons per cubic yard) | Volume at 10 ft × 10 ft × 3 in | Weight on that basis |
|---|---|---|---|
| Crushed stone | 1.5 | 0.93 cubic yards | 1.39 tons |
| Pea gravel | 1.35 | 0.93 cubic yards | 1.25 tons |
| River rock | 1.4 | 0.93 cubic yards | 1.30 tons |
| Decomposed granite | Not stated on the linked calculators | 0.93 cubic yards | Not calculated here; ask the supplier for its density |
Worked example: full arithmetic
For the 10-foot by 10-foot area at 3 inches deep, used in the table:
- Area: 10 × 10 = 100 square feet.
- Depth in feet: 3 ÷ 12 = 0.25 feet.
- Volume in cubic feet: 100 × 0.25 = 25 cubic feet.
- Volume in cubic yards: 25 ÷ 27 = 0.926 cubic yards, rounded to 0.93 cubic yards.
- Crushed stone weight: 0.93 × 1.5 = 1.395 tons, rounded to 1.39 tons as shown on the Gravel Calculator.
- Pea gravel weight: 0.93 × 1.35 = 1.2555 tons, rounded to 1.25 tons as shown on the Pea Gravel Calculator.
- River rock weight: 0.93 × 1.4 = 1.302 tons, rounded to 1.30 tons as shown on the Decorative Rock Calculator.
Depth changes the result in proportion: at 2 inches the same area needs 100 × (2 ÷ 12) ÷ 27 = 0.62 cubic yards, and at 4 inches it needs 100 × (4 ÷ 12) ÷ 27 = 1.23 cubic yards, before any allowance for uneven ground. Check your own area and depth in the Gravel Calculator rather than scaling a tonnage from a different depth.
Frequently asked questions
Which gravel is best for a walking path? Crushed stone and decomposed granite pack into firmer paths than loose pea gravel or river rock, but the right choice depends on drainage, edging, and how the path will be used.
Can I use river rock for a driveway? River rock is mainly decorative and does not lock together, so it is not a stable driving surface on its own.
Why does the same area need different tonnages? Because the densities differ: a cubic yard of crushed stone at 1.5 tons per cubic yard weighs more than the same volume of pea gravel at 1.35 tons per cubic yard, on the calculators’ stated basis.
Should I add extra for uneven ground? Yes, allow for uneven ground and spillage, and confirm the allowance with the supplier, especially on a sloped or irregular area.
Planning-only disclaimer: This guide is for planning only. Densities vary by source and product, so confirm the density, depth, and quantity with your supplier before ordering, and check drainage and local rules for the area you are covering.