Landscaping
Mulch Calculator
Work out cubic metres of mulch from your bed area and preferred depth.
How this calculator works
Enter your garden bed area, or dimensions and the calculator finds the area for you, including circular beds. It multiplies area by depth to get cubic metres, then adds 10 percent for settling.
Mulch is light but bulky. The calculator converts to tonnes using typical densities, 0.35 to 0.5 tonnes per cubic metre depending on the mulch, mostly so you can check what fits in a trailer or ute.
It also counts 50 litre bags and compares the cost against a bulk delivery so you can pick the cheaper option for your quantity.
| Situation | Depth | Why |
|---|---|---|
| Ornamental beds | 50mm to 75mm | Weed suppression and moisture retention |
| New plantings | 75mm | Keep mulch clear of stems and trunks |
| Weed-prone areas | 75mm to 100mm | Thicker layers block light better |
| Around established trees | 75mm to 100mm | Out to the drip line if possible |
More than 100mm can stop rain reaching the soil, deeper is not better.
| Depth | Coverage |
|---|---|
| 50mm | 20 m² |
| 75mm | 13.3 m² |
| 100mm | 10 m² |
Frequently asked questions
How much area does a cubic metre of mulch cover?
At the recommended 75mm depth, one cubic metre covers about 13 square metres. At 50mm it stretches to 20 square metres.
How many bags of mulch make a cubic metre?
Twenty standard 50 litre bags equal one cubic metre. Past 8 or 10 bags, a bulk delivery is usually cheaper and saves the plastic.
What depth should mulch be?
50mm to 75mm suits most garden beds. Go closer to 100mm for weed-prone areas, but avoid piling mulch against plant stems and tree trunks because it causes rot.
How much does bulk mulch cost in Australia?
Typically $45 to $85 per cubic metre delivered as at July 2026, depending on type and area. Fine decorative barks cost more, coarse hardwood chip less. Some councils sell chipped green waste cheaply or free.
When is the best time to mulch?
Late spring, after the soil has warmed and while it still holds moisture. A second lighter top-up in autumn keeps the layer at depth through winter.
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