How much decomposed granite do I need?
Decomposed granite, DG at the yard, is granite weathered down to gravel and grit that packs into a firm surface you can walk on and wheel a barrow over, at a fraction of what pavers cost. It is sold by the cubic yard and by the ton, and the one thing to know before you order is that it compacts: the depth you lay is not the depth you end up with.
Decomposed granite calculator
How much decomposed granite do you need?
Working out a whole yard rather than one bed? Sketch it to scale in the planner and every area is measured, costed and totalled together.
The formula, with the compaction
cubic yards = (square feet × depth in inches) ÷ 324
DG loses about a quarter of its depth under a plate compactor. A path that wants to finish at three inches is laid at four, and that is the number to put in the box: it is the loose material you buy, not the packed surface you walk on. A 4 by 30 ft path laid at 4 inches is (120 × 4) ÷ 324 = 1.5 cubic yards, or about 2.3 tons, and it finishes at three.
| Use | Finished depth | Lay at | Under it |
|---|---|---|---|
| Ground cover between plants | 2 in | 2–3 in | Fabric |
| Garden path | 3 in | 4 in | Fabric, edging |
| Patio or seating area | 3 in | 4 in | 2–3 in of compacted base, edging |
| Driveway | 4 in | 5–6 in | 4 in of compacted base, edging |
Loose or stabilized
Plain DG packs well but it is still loose stone: it tracks into the house on shoes, washes in a heavy rain, and grows a crust of weeds if it is not walked on. Stabilized DG has a binder mixed in that sets the surface once it is wetted and compacted, so it stays put on a slope and sweeps clean. It costs roughly half again as much by the yard, and it is the right choice for a patio, a path with any fall on it, or anywhere near a door. Loose is fine as ground cover between plants and for a level path out in the yard.
Neither one is resin-bound or paved. DG is a surface you rake once a year and top up every few, and that is the trade for costing what it does.
What goes underneath
A path on well-drained ground can go straight onto compacted soil with fabric under it. A patio, or any path on clay, wants two or three inches of compacted crushed base first, the same way a paver patio does, or the DG pumps up through the mud in the first wet winter. A driveway wants four.
Edging is not optional. DG spreads at the edges under foot, and without a hard edge a three foot path is four feet wide and two inches deep within a couple of years. Steel edging is the usual choice because it can follow a curve.
What it costs
Loose, decomposed granite runs about $45 – $95 per cu yd, with the colour setting the price: the common gold is at the bottom of the range and the greys and reds above it. Stabilized adds roughly half. By the ton, divide by about 1.5. Bagged, at $7 – $10 for half a cubic foot, it comes to $378 – $567 a yard, so bags are for topping up, not for laying a path.
Delivery is $50 – $150 a load with a 2 yard minimum, and a plate compactor is a day's rental, which is worth it: DG that is only raked and hosed never firms up, and a firm surface is the whole point.
For a patio, the same footprint in pavers is $12 – $28 per sq ft before the base, and in poured concrete $6 – $14 per sq ft. DG is the cheapest surface that still reads as a patio, and the patio cost guide puts the three side by side.
Quick checklist
- Decide the finished depth by use, then add a quarter for compaction: lay at four to finish at three.
- Convert with the 324 rule, and to tons at about 1.5 a yard.
- Stabilized for patios, slopes and near doors; loose for ground cover and a level path.
- Fabric under everything, a compacted base under a patio, edging around all of it.
- Rent the plate compactor. Wet the DG before you run it.
The Path tool paints a run of DG at the width you set, round whatever curve you draw, and the planner works out the cubic yards, the tons and the cost for your state. The side yard path and the low-water front yard examples both use it.