Loose stone vs. compacted DG: why this is one page, not two
Crushed stone (often sold as #57) and decomposed granite are both crushed rock, and both show up as material options on the gravel calculator. What separates them in practice isn't the rock, it's how they're used. Crushed stone is almost always used loose: it drains well, it doesn't need to be compacted into a solid surface, and jobs like French drains, drainage layers, and gravel bases lean on that looseness on purpose. Decomposed granite is the opposite case. It's spread, wetted, and compacted with a plate compactor into a firm, almost packed-dirt surface meant to be walked or driven on directly, for garden paths and patios. That difference changes the math: DG needs extra material ordered up front to account for the volume it loses once compacted, and crushed stone generally does not. This calculator keeps that compaction allowance as its own separate field from the general waste buffer, because they solve different problems and conflating them under-orders one or the other.
Why compaction eats volume
Loose aggregate has air gaps between the particles. Compacting it, whether with a plate compactor, a hand tamper, or just repeated foot and vehicle traffic over time, presses those particles closer together and drives the air out, which shrinks the total volume even though no material has actually left the site. Decomposed granite in particular is installed as a loose top layer and then deliberately compacted to create its signature firm, walkable surface, and that process typically reduces the loose volume by about 10 to 25 percent depending on the DG blend, how much it's dampened before compacting, and how thoroughly it's tamped. If you order and spread exactly the cubic yardage that matches your target finished depth, you will end up with a layer noticeably thinner than planned once it's compacted, because a chunk of that ordered volume compressed into the gaps rather than staying at the surface.
How to layer a DG path or patio
A durable DG surface is rarely just DG on bare ground. The typical build is a compacted base layer, often crushed stone or a road-base blend, topped with 2 to 3 inches of DG that is itself compacted to its finished depth. The base gives the path structure and drainage; the DG top gives the walkable surface and the material's characteristic look and feel. Both layers benefit from working in thin lifts, spreading a couple of inches at a time and compacting each lift rather than piling the full depth and compacting once, which tends to leave the bottom under-compacted. Lightly wetting the DG before compaction also helps the fines bind together into a firmer surface, rather than staying loose and prone to raveling underfoot.
Crushed stone for drainage and base
Crushed stone, particularly the angular, washed #57 grade, is the standard choice anywhere water needs to move through the material rather than sit on top of it: French drains, drainage trenches, and the gravel layer under a paver or slab installation. Because it's meant to stay loose and permeable, there's no compaction allowance to add here, order to your target depth plus a normal waste buffer for spillage and uneven ground. Crushed stone also serves as the compacted base course under driveways and DG paths alike, in that specific role it is compacted like the DG layer above it, so the compaction allowance would apply there instead, on the base course rather than on loose drainage stone. The toggle on this calculator sets a sensible default compaction percentage per material, but the field itself is always editable, since the right number really depends on what you're building, not just what the material is called.
Depth and ordering extra
Depth follows the job: a DG garden path commonly runs 2 to 3 inches of finished, compacted depth; a driveway base typically runs 4 to 6 inches; drainage stone around a French drain pipe is often built around 12 inches. Whatever the target, remember that two separate allowances stack on top of it: the waste buffer (5 to 15 percent, for spillage and uneven ground, the same as any bulk material) and, for compacted material only, the compaction allowance (10 to 25 percent, to reach that finished depth after settling). Ordering only for waste on a compacted job is the most common way a DG path or a driveway base comes up visibly short once it's been tamped down.
If your project is decorative ground cover or a shallow drainage bed rather than a compacted surface, the gravel calculator covers the broader range of aggregate materials at typical decorative depths. For a French drain or dry creek bed specifically, the river rock calculator is built around those drainage depths. If the job is setting pavers rather than a stone surface on its own, the sand calculator handles the bedding layer underneath.