Getting the right amount of mulch comes down to area and depth: length × width × depth gives cubic metres, and multiplying by the mulch’s bulk density gives tonnes. Use the calculator below for four popular Australian mulches — a 75mm layer is the standard for garden beds, suppressing weeds while holding moisture in the soil.
Mulch Calculator
How much mulch do you need? Enter your area below — results in cubic metres & tonnes.
Estimates use typical bulk densities shown above. Actual density varies by supplier and moisture — confirm with your landscape supplier before ordering. How our calculators work
How to use the mulch calculator
- Measure your garden bed and enter the length, width and depth in metres — 0.075m (75mm) is the standard mulch depth.
- Pick your mulch type — each uses its typical Australian bulk density, e.g. hardwood chip at 0.5 t/m³.
- Leave the 10% extra box ticked to cover settling and wastage, then hit Calculate for your volume, weight and bag count.
FAQs
How deep should mulch be in a garden bed?
75mm is the standard recommendation — deep enough to suppress weeds and hold moisture, without smothering plant stems.
How many tonnes are in a cubic metre of mulch?
About 0.5 t for hardwood chip, 0.4 t for pine bark, 0.3 t for sugar cane mulch and 0.45 t for cypress mulch.
Does mulch really stop weeds?
A 75mm layer blocks the light weed seeds need to germinate, and it keeps the soil moist so your plants establish faster and outcompete weeds.