How Much Crusher Dust Do I Need? Tonnes by Area and Depth

For a 50–100 mm compacted layer, plan on about 0.1 tonnes of crusher dust per square metre at 50 mm, 0.15 t at 75 mm and 0.2 t at 100 mm. A 10 m² area at 75 mm takes about 1.5 tonnes (0.9 m³). Those figures include 20% extra for compaction and use about 1.7 tonnes per m³, worked out from a supplier's bag weight and volume. The charts below give tonnes and bags for paths, pads and bases.

What is crusher dust?

Crusher dust is the fine material left over when rock is crushed: particles from a few millimetres down to dust. Because it has a mix of sizes, it packs down hard. Suppliers in Australia sell it by the tonne or in bags, as "crusher dust", "blue metal dust" or "blue base". IDLVR describes it as a fine, minus-graded quarry product that "compacts tightly to form a firm, level base under pavers, slabs, and concrete". In North America, similar material goes by other names; Angi lists decomposed granite, rock dust, breeze and chat, and you'll also see stone dust and screenings.

How much crusher dust do I need?

Work it out in three steps: area × depth gives the compacted volume; add 20% because the loose dust packs down; multiply by the weight per cubic metre to get tonnes.

Crusher dust by area and depth (with 20% for compaction)
Area	50 mm	75 mm	100 mm
5 m²	0.3 m³ · 0.5 t	0.45 m³ · 0.8 t	0.6 m³ · 1 t
10 m²	0.6 m³ · 1 t	0.9 m³ · 1.5 t	1.2 m³ · 2 t
15 m²	0.9 m³ · 1.5 t	1.35 m³ · 2.3 t	1.8 m³ · 3.1 t
20 m²	1.2 m³ · 2 t	1.8 m³ · 3.1 t	2.4 m³ · 4.1 t
30 m²	1.8 m³ · 3.1 t	2.7 m³ · 4.6 t	3.6 m³ · 6.1 t
50 m²	3 m³ · 5.1 t	4.5 m³ · 7.7 t	6 m³ · 10.2 t
100 m²	6 m³ · 10.2 t	9 m³ · 15.3 t	12 m³ · 20.4 t

Suppliers deliver loose crusher dust by the tonne, often with a minimum load. If your answer is just under a whole tonne, round up: a little left over is better than a thin patch.

How deep should crusher dust be?

Suppliers give a range of 50 to 100 mm. iSeekplant says a 50 mm layer is usually enough for light foot traffic and suggests up to 100 mm for driveways or heavier traffic. Nuway gives the same 50–100 mm "depending on application" for its bagged crusher dust. Compact each layer thoroughly; iSeekplant notes the fine particles are what make it compact well.

Typical crusher dust depths
Use	Depth	Note
Garden path, light foot traffic	50 mm	iSeekplant
Base under a slab or shed	75–100 mm	Thicker on soft or wet ground
Driveway or heavier traffic	Up to 100 mm	iSeekplant; a road base layer is often used underneath

How many bags of crusher dust?

Nuway sells crusher dust in 25 kg bags of 14.7 litres, and says 68 bags make 1 m³. That's the figure we use to work out the weight per cubic metre (25 kg ÷ 14.7 L = 1.7 kg per litre). Bags for small areas, with 20% for compaction:

25 kg bags of crusher dust (14.7 L each)
Area	50 mm	75 mm	100 mm
1 m²	5	7	9
2 m²	9	13	17
4 m²	17	25	33
6 m²	25	37	49

Bags are handy for a small pad or a path repair. Past about 1 m² at 100 mm (9 bags, over 0.2 tonnes to carry), loose delivery by the tonne is usually cheaper and far less work.

Can you use crusher dust under pavers?

This is where suppliers disagree, so check with your paver maker before you start. IDLVR markets crusher dust as a base under pavers and slabs and as a bedding layer or screed. iSeekplant says it's "not generally recommended for use directly under pavers", and mentions stabilising it with cement if it's used as the final layer. In practice:

As a sub-base under pavers, compacted in layers, crusher dust is widely used in Australia.
As the bedding layer right under the pavers, follow your paver maker's instructions. Many paver guides specify washed bedding sand instead, because it drains freely. Our paver base and sand guide covers the North American layer system.

Crusher dust in tons (US units)

For stone dust or screenings bought by the US ton, at the same weight and 20% compaction allowance:

Stone dust by area, in US tons
Area	2 in	3 in	4 in
50 sq ft	0.53 tons	0.8 tons	1.06 tons
100 sq ft	1.06 tons	1.59 tons	2.12 tons
200 sq ft	2.12 tons	3.19 tons	4.25 tons
400 sq ft	4.25 tons	6.37 tons	8.49 tons

Worked example: a garden path

A path 12 m long and 1.2 m wide: 12 × 1.2 = 14.4 m².
Depth 75 mm: 14.4 × 0.075 = 1.08 m³ compacted.
Add 20% for compaction: 1.3 m³ loose.
Weight: 1.3 × 1.7 = 2.2 tonnes. Order 2.5 tonnes.

Worked example: a pad for a garden shed

A 3 × 3 m pad: 9 m².
At 100 mm with 20%: 9 × 0.1 × 1.2 = 1.08 m³.
Weight: about 1.8 tonnes, or 74 bags of 25 kg if you buy bagged.

How many square metres does a tonne of crusher dust cover?

Turn the numbers around to see how far each tonne goes, at about 1.7 t/m³ and with 20% for compaction:

Area one tonne of crusher dust covers
Compacted depth	Area per tonne	Area per 25 kg bag
50 mm	9.8 m²	0.25 m²
75 mm	6.5 m²	0.16 m²
100 mm	4.9 m²	0.12 m²
150 mm	3.3 m²	0.08 m²

So a tonne makes about 10 m² of path at 50 mm, or about 5 m² of pad at 100 mm.

Ordering checklist

Ask how it's sold. By the tonne, by the cubic metre, or in bulk bags. Convert with your supplier's weight per cubic metre if they give one.
Check the minimum load. Many yards have a minimum delivery, which can make a small job cheaper in bags.
Plan the drop spot. A tonne of crusher dust is a pile you can't move far by hand in an afternoon. Have it tipped as close to the job as the truck can safely get.
Hire a plate compactor. Crusher dust needs proper compaction to set up hard. Damp it lightly if it's very dry; it compacts better than bone-dry dust.
Cover the pile. Rain washes fines out of an open stockpile.

Crusher dust or road base?

Road base is a coarser crushed rock with fines, typically used as the structural layer under driveways and slabs. Crusher dust is finer and gives a smoother, tighter top. A common approach for heavier jobs is road base underneath and crusher dust on top for a smooth finish. For coarser gravels, use the gravel calculator, where you can enter your supplier's weight per cubic metre.

Why does the weight vary?

We use 1.7 t/m³ from Nuway's bagged figures. Loose crusher dust from a stockpile can weigh a little less per cubic metre, and wet material weighs more. Our gravel calculator uses 1.6 t/m³ for crushed stone and sand. If your supplier quotes their own figure, use it: tonnes = cubic metres × their weight per m³.

Common mistakes

Forgetting compaction. 75 mm of compacted crusher dust starts as about 90 mm of loose material.
Laying it all at once. Compact in layers. A thick single layer never firms up at the bottom.
Mixing up tonnes and cubic metres. A cubic metre of crusher dust weighs more than a tonne. Ordering "2 cubic metres" and "2 tonnes" gets you different amounts.
No edging. Paths and pads need an edge to stop the dust spreading and washing out.