Mulch Calculator
Enter your garden bed dimensions and the depth you want to spread, and get the mulch volume in cubic metres and litres — whether you are ordering a bulk delivery or grabbing bags from the nursery.
Enter your measurements
Your m³ of mulch result will appear here instantly.
How to use this calculator
- 1
Measure the length and width of each garden bed in metres.
- 2
For irregular beds, break them into rough rectangles and add the results together.
- 3
Choose your depth: 75–100 mm is the sweet spot for most mulches — deep enough to suppress weeds, shallow enough to let rain through.
- 4
Buy bulk mulch by the cubic metre for large jobs, or compare against bag quantities for small beds.
- 5
Top up garden beds with fresh mulch every 12 months or so as it breaks down.
How the calculation works
Volume
Bed length × width × depth gives cubic metres. A 10 mm depth is 0.01 m, so a 6 m × 2 m bed at 75 mm needs 6 × 2 × 0.075 = 0.9 m³.
Litres and weight
One cubic metre is 1,000 litres. Bagged mulch is typically sold in 25–50 L bags. The approximate weight uses a typical dry bulk density of about 400 kg/m³ — actual weight varies a lot by mulch type and moisture.
Worked example
A front-garden bed 6 m long × 2 m wide, mulched to 75 mm.
Volume = 6 × 2 × 0.075 = 0.9 m³ = 900 litres.
Order 1 m³ of mulch from a landscape supplier, or about 18 × 50 L bags from the nursery.
Frequently asked questions
How deep should mulch be?
75–100 mm (7.5–10 cm) is the standard recommendation for Australian garden beds — enough to suppress weeds and hold moisture without sealing out rain. Keep it around 50 mm over garden beds with fine or drought-sensitive plants, and never pile mulch against tree trunks or house walls (leave a gap of 10–15 cm).
How many bags of mulch make a cubic metre?
Twenty bags of 50 L, or forty bags of 25 L, equal one cubic metre. Bulk mulch from a landscape yard is much cheaper per cubic metre — usually a fraction of the bagged price — but you need somewhere for the pile to go and a way to move it.
Does mulch type change the amount I need?
The volume maths is the same, but chunky barks and wood chips settle less than fine mulches and sugarcane, which compact over a season. If in doubt for fine mulches, aim for the top of the depth range and expect to top up sooner.
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Results are estimates only. Always confirm material requirements with your supplier or a qualified professional before purchasing.