How the gravel calculator works
You measure a gravel job in area and depth, but a quarry or builders' merchant sells it by the tonne, the US ton or the bulk bag. The calculator first finds the volume of the layer, adds a margin for stone that settles into the soil and spreads past the edges, then multiplies by the bulk density of the material you picked.
Weight = length × width × depth × (1 + margin) × densityBulk density is the weight of a cubic metre of loose stone including the air between the pieces, so rounded stones of one size weigh less per cubic metre than a graded mix whose fines fill the gaps. That is why the same volume of crusher run can weigh nearly half as much again as clean crushed stone. One US ton is 2,000 lb (907 kg), about 10% less than a metric tonne, and the calculator switches between them with the unit toggle.
Worked example
A front garden bed 5 m × 3 m finished with 5 cm of pea gravel holds 5 × 3 × 0.05 = 0.75 m³. With a 10% margin you need 0.825 m³, and at 1.6 t/m³ that weighs 1.32 tonnes. In 25 kg bags that is 1,320 ÷ 25 = 52.8, so 53 bags, though at this size two 1-tonne bulk bags (or a small loose delivery) are usually cheaper and easier; one bulk bag of 0.5–1 t is not enough. At this depth each tonne covers 12.5 m². The same bed in US units, 16 × 10 ft at 2 in, takes about 1.09 yd³ or 1.46 US tons, which is 59 half-cubic-foot bags.
Densities of common gravels
| Material | t per m³ | US tons per yd³ | Typical use |
|---|---|---|---|
| Pea gravel / shingle (6–10 mm, rounded) | 1.6 | 1.35 | Paths, beds, play areas |
| Clean crushed stone, #57 or 20 mm | 1.45 | 1.22 | Drainage, French drains, driveway top |
| Crusher run / MOT Type 1 (compacted) | 2.1 | 1.77 | Sub-base for patios and drives |
| Decomposed granite | 1.7 | 1.43 | Paths, xeriscape, stabilised surfaces |
| River rock / cobbles (50–150 mm) | 1.5 | 1.26 | Dry creek beds, borders |
Wet stone is heavier and moisture varies by load, so treat these as planning figures. If your supplier quotes a density for the exact product, use that instead.
Choosing the right depth
- Decorative beds: 4–5 cm (1.5–2 in) over a weed membrane hides the fabric without the stones rolling underfoot.
- Footpaths: 5 cm of pea gravel or decomposed granite on a compacted base; thicker loose layers feel like walking on a beach.
- Driveways: 10–15 cm (4–6 in) of compacted crusher run topped with 5–8 cm of clean angular stone that locks together under tyres.
- Rule of thumb: make any loose layer at least twice as deep as the largest stone, so 20 mm gravel needs 4 cm or more.
Buying tips
Bulk bags usually hold between roughly half a tonne and one tonne, depending on the supplier, so check the stated weight before comparing prices. Loose deliveries by the tonne are cheaper still for anything above two or three tonnes, but need a clear place to tip. Order all the stone from one delivery where you can: colour and grading change between quarry batches.
Frequently asked questions
How much does a cubic yard of gravel weigh?
Most loose gravel weighs 1.2 to 1.4 US tons per cubic yard (2,400–2,800 lb). Compacted crusher run is heavier, about 1.75 US tons per cubic yard.
How many square feet does a ton of gravel cover?
At 2 in deep, one US ton of pea gravel covers about 120 ft²; at 3 in it covers about 80 ft². Deeper layers cover proportionally less.
How much gravel do I need for a 12x24 driveway?
A 12 × 24 ft driveway is 288 ft². A 4 in layer of crushed stone is 3.56 yd³, about 4.3 US tons at 1.22 tons per yd³, or 4.8 tons with a 10% margin.
How many tonnes of gravel per square metre?
At 5 cm depth, pea gravel needs about 0.08 tonnes per square metre, so one tonne covers 12.5 m². At 10 cm it is 0.16 tonnes per m².
Should I put anything under gravel?
On a garden bed or path, a permeable weed membrane stops the stones sinking into the soil. Driveways need a compacted sub-base of crusher run under the top stone.
Last reviewed: 2026-09-27 · How we calculate