Mulch Calculator Australia: How Much Mulch Do I Need?
Enter your bed size and depth to get cubic metres, litres, bags and weight for sugarcane, pea straw, wood chip and more. Built for Australian gardens.
Your mulch requirements
How many bags to buy
Buying more than about 1 m³? Bulk delivery by the cubic metre is often better value than bags. Check with your local landscape supplier.
Estimated weight
The Australian gardener's guide to mulch
Across Australia, from tropical Queensland to dry South Australian summers, mulch is one of the simplest ways to look after a garden. A good layer of mulch slows evaporation from the soil, suppresses weeds, moderates soil temperature and, if it's organic, feeds the soil as it breaks down.
Saves water
Mulch shields the soil from sun and wind, so moisture stays in the root zone longer. That means less watering in summer.
Fights weeds
A 75 to 100mm layer blocks light from reaching weed seeds, cutting down the time you spend weeding.
Protects roots
A mulch layer helps buffer soil temperature swings, which protects roots during hot spells and cold snaps.
Bushfire-prone areas
If your property is in a bushfire-prone area, check local council or fire authority guidance. Non-combustible mulch such as gravel is often recommended close to buildings.
Mulch types compared
| Mulch | Best for | Suggested depth | Approx. weight |
|---|---|---|---|
| Sugarcane | Veggie beds, general use | 50–75mm | ~120 kg/m³ |
| Lucerne | Edible gardens | 50–75mm | ~130 kg/m³ |
| Pea straw | Raised beds, veggies | 50–75mm | ~110 kg/m³ |
| Wood chip | Trees, paths, natives | 75–100mm | ~400 kg/m³ |
| Pine bark | Ornamental beds | ~75mm | ~350 kg/m³ |
| Gravel / pebbles | Dry gardens, succulents | ~50mm | ~1,600 kg/m³ |
Weights are approximate and vary with moisture content and product. Treat them as a guide for planning loads and deliveries.
How to calculate how much mulch you need
Multiply the area of your bed (length × width, in metres) by the depth you want (in metres). For example, a 3m × 1.2m bed at 75mm deep is 3 × 1.2 × 0.075 = 0.27 m³, or 270 litres. That is roughly nine 30-litre bags. The calculator above does this for you, including circular and triangular beds.
Frequently asked questions
How deep should mulch be in Australia?
About 75mm (7.5cm) suits most garden beds. Go to 100mm where weeds are a problem, and stay around 50mm in vegetable gardens where you want easy access to the soil. Keep mulch a few centimetres clear of plant stems and trunks to avoid rot.
What mulch is best for veggie gardens in Australia?
Pea straw, lucerne and sugarcane mulch are popular choices. They are light, easy to spread and break down over a season to add organic matter to the soil.
How often should I top up mulch?
Organic mulches generally need topping up once or twice a year. Check the depth in spring and autumn, and top up when the layer drops below about 50mm. Woody mulches such as bark and wood chip tend to last longer than straw-type mulches.
Can I put mulch over weeds?
A thick layer of mulch smothers many annual weeds. For persistent perennial weeds, lay damp cardboard or several sheets of newspaper over the area first, then cover with mulch.
How much does mulch cost?
Prices vary by type, supplier and location. Bagged mulch is convenient for small jobs, while bulk delivery by the cubic metre is usually more economical for larger areas. Get a quote from a local supplier for current pricing.
Brought to you by Garden Yard Australia, your Australian garden and outdoor living store.
Results are estimates based on typical mulch densities. Actual needs vary with product, moisture and how evenly it is spread.