Short answer
A 6 x 1.5 m garden bed (9 m²) mulched 75 mm deep needs 0.68 m³ of mulch, or about 0.74 m³ with 10% spare. That is roughly 19 bags of 40 L, or one 1 m³ bulk delivery, about 0.3 tonnes. The sum is area x depth, plus an allowance for settling. One cubic metre covers 20 m² at 50 mm, 13.3 m² at 75 mm and 10 m² at 100 mm. The calculator below does it for soil, mulch, sand, gravel, pebbles and road base.
Use this free calculator to work out how much garden soil, topsoil, mulch, sand, gravel, pebbles or road base you need, in cubic metres, tonnes and bags, with an indicative bulk and bagged price. Measure a bed by length and width, or enter an area for an irregular shape.
Soil, mulch and gravel calculator
Volumes are calculated exactly from your sizes. Weights are typical values that vary with moisture and grade, and prices are indicative supplier list prices that vary by city, product and delivery. Ranges reviewed October 2026.
How to calculate soil, mulch and gravel
- Volume: area (m²) x depth (m). A 75 mm layer is 0.075 m deep.
- Allowance: add about 10% for soil and mulch, and 10 to 20% for gravel and road base, because loose material settles and compacts.
- Weight: volume x density in tonnes per cubic metre. Mulch is light and gravel is heavy, so a cubic metre of gravel weighs several times more than a cubic metre of mulch.
- Bags: volume in litres ÷ bag size. A cubic metre is 1,000 litres.
| Depth | Area covered by 1 m³ |
|---|---|
| 25 mm | 40 m² |
| 50 mm | 20 m² |
| 75 mm | 13.3 m² |
| 100 mm | 10 m² |
| 150 mm | 6.7 m² |
| 200 mm | 5 m² |
| Example | Volume with allowance | Weight | Bags |
|---|---|---|---|
| Mulch, 6 x 1.5 m bed at 75 mm | 0.74 m³ | 0.3 t | 19 x 40 L |
| Garden soil, 4 x 2 m new bed at 200 mm | 1.76 m³ | 2.3 t | 44 x 40 L |
| 20 mm gravel, 10 x 1 m path at 75 mm | 0.86 m³ | 1.3 t | about 65 x 20 kg |
| Topsoil, 5 x 4 m lawn at 100 mm | 2.20 m³ | 3.1 t | 55 x 40 L |
| Road base, 4 x 3 m paver base at 100 mm | 1.44 m³ | 2.5 t | bulk |
| Paver bedding sand, same area at 30 mm | 0.40 m³ | 0.6 t | about 30 x 20 kg |
How deep should each material be?
| Use | Typical depth |
|---|---|
| Mulch on garden beds | 50 to 75 mm (some guides say up to 100 mm) |
| New garden bed, soil | 200 to 300 mm |
| Topping up an existing bed | 50 to 100 mm |
| Soil under new turf | 100 mm (100 to 150 mm for underlay) |
| Lawn top-dressing | 10 to 25 mm |
| Decorative gravel or pebbles | 30 to 75 mm |
| Compacted gravel path | 75 to 100 mm |
| Road base under pavers or a driveway | 100 mm, up to about 150 mm for a driveway |
| Paver bedding sand | 25 to 30 mm |
Depths come from supplier guides such as Elite Sand and Soil and Melbourne landscape suppliers, and councils and manufacturers specify their own, so follow the instructions for your pavers or turf.
How much does a cubic metre weigh?
Weights vary with moisture and grade, and these are typical values from suppliers including Australian Native Landscapes and Elite Sand and Soil. The calculator uses the figure in the last column.
| Material | Range from suppliers | Calculator uses |
|---|---|---|
| Garden soil mix | 1.2 to 1.3 t/m³ | 1.3 |
| Topsoil or turf underlay | 1.3 to 1.5 t/m³ | 1.4 |
| Mulch (bark, woodchip) | 0.3 to 0.5 t/m³ | 0.4 |
| Sand | 1.3 to 1.6 t/m³ | 1.5 |
| 20 mm gravel or blue metal | 1.45 to 1.6 t/m³ | 1.5 |
| Decorative pebbles | about 1.5 t/m³ | 1.5 |
| Road base (DGB20) | about 1.6 to 1.75 t/m³ loose, about 2.4 compacted | 1.75 |
Bulk or bagged: prices and minimums
Bulk material is sold by the cubic metre (sometimes by the tonne), usually with a minimum of about 1 m³ and a delivery fee. Bagged material is priced by the litre or kilogram and suits small jobs.
| Supplier list prices per m³ | Examples |
|---|---|
| Sydney Landscape Supplies (Sydney) | garden mix $139 to $159; pine bark $159; hardwood chip $189 |
| Builto (Melbourne), including GST, 1 m³ minimum | 3-way soil $102.59; black mulch $99.14; 20 mm crushed rock $99.36; brick sand $173.88 |
| SA Landscape Supplies (Adelaide), including GST | pine bark $133; veggie and garden soil $193; Jeffries mulches $132 to $166 |
We did not find a published bulk price list for Perth, and pebble prices range from about $90 to $500 a cubic metre depending on the stone, so ask suppliers for a quote. Delivery is typically $50 to $120 a load, and a truck often carries only about 3 m³ of gravel, 4 m³ of soil or 8 m³ of mulch, so large jobs can mean several loads. Bagged soil and mulch at hardware stores works out at roughly $0.20 to $0.30 a litre, or about $190 to $300 a cubic metre, from Bunnings listings seen in search results. Check current prices before you buy.
For paving and decking projects, see the concrete calculator and the decking calculator, and for labour see landscaper rates.
Safety and quality
- Asbestos in mulch: check for pieces of cement sheet or fibrous bits and keep mulch damp when spreading it. See WA Health and the NSW EPA, and report suspect material to your state EPA.
- Certified products: AS 4454 covers composts, soil conditioners and mulches, and AS 4419 covers soils for landscaping, and many suppliers sell certified products.
- Bushfire areas: CSIRO advises keeping combustible mulch away from windows, doors and subfloors, avoiding very fine mulch, and using gravel or pebbles near the house.
- Termites and damp: keep garden beds clear of walls and keep the slab edge and weep holes visible, as building inspectors advise.
- Handling: damp bags can weigh around 30 kg, so lift with care, and wear a dust mask when spreading dry soil or sand.
Common mistakes
- Ordering the exact volume. Soil and mulch settle and gravel compacts, so add 10 to 20%.
- Burying trunks and walls. Mulch piled against a trunk or house wall holds moisture, so keep it clear.
- Mixing up tonnes and cubic metres. Some suppliers sell by the tonne, so compare prices on the same unit.
- Forgetting delivery limits. Check the minimum order, the delivery fee and whether the truck can reach your site.
- Skipping the base. Paths and paving need a compacted road base, not just sand.
- Using the wrong depth. Too thin and mulch does not suppress weeds. Too thick and it smothers plants.
Frequently asked questions
How much mulch do I need for 10 m²?
At a typical 75 mm depth, 10 m² needs 0.75 m³, or 0.83 m³ with 10% spare. That is about 21 bags of 40 L, or a bulk delivery, which suppliers usually sell from 1 m³.
How many bags of mulch or soil make a cubic metre?
A cubic metre is 1,000 litres, so it takes 25 bags of 40 L, 20 bags of 50 L or 40 bags of 25 L. A damp 40 L bag of garden mix can weigh around 30 kg, so bulk delivery is easier for anything over about half a cubic metre.
How much does a cubic metre of soil weigh?
Roughly 1.2 to 1.4 tonnes for garden mix and topsoil, depending on moisture. Mulch is much lighter at about 0.3 to 0.5 tonnes, sand and gravel are around 1.5 tonnes, and road base is about 1.75 tonnes loose (and about 2.4 tonnes once compacted).
How deep should mulch be?
Most guides say 50 to 75 mm for garden beds, and some suggest up to 100 mm. Keep mulch clear of tree trunks and away from house walls, and use a thinner layer for fine mulches. Better Homes and Gardens suggests keeping it 10 to 15 cm from the trunk.
How much gravel do I need for a path?
A 10 x 1 m path at 75 mm is 0.75 m³. With a 15% allowance, order about 0.86 m³, roughly 1.3 tonnes. Put the gravel over a compacted base for a firm path.
How much soil do I need for a new lawn?
New turf needs about 100 mm of soil underneath, and some suppliers suggest 100 to 150 mm of underlay. A 5 x 4 m lawn (20 m²) at 100 mm is 2.00 m³, so order about 2.20 m³ with 10% spare.
Is there asbestos in bulk mulch?
It has happened. NSW has had a mulch order since 2016 requiring processors to keep mulch free of asbestos, and WA Health says mulch must be visibly free of asbestos when sold. Look for pieces of cement sheet or fibrous fragments, keep the mulch damp when spreading it, be careful with free or unlabelled mulch, and report suspect material to your state EPA.
Related tools
- Landscaper rates - paving, retaining walls, turf and irrigation
- Concrete calculator - slabs, paths and post holes
- Decking calculator - boards, joists and cost
- Renovation quote comparator - paste landscaping quotes for red-flag analysis
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