Mulch calculator
Enter the area and depth — we’ll convert it to cubic metres and bulk bags (a mulch bulk bag holds ≈ 1 m³).
The depth that actually saves water
75 mm is the sweet spot — deep enough to stop evaporation and suppress weeds, shallow enough that rain and retic still get through. At 75 mm, one cubic metre covers about 13 m², so a one-tonne bulk bag does a typical Perth front-garden bed run.
Which mulch for which job
Chunky pine bark is the all-rounder: it lasts 2–3 years and lets water through. Lupin mulch — a WA specialty — feeds the soil as it breaks down, which sandy Perth beds desperately need; use it around natives, roses and vegies. Black feature mulch looks sharp on display beds but check it's a composted product, not dyed rubbish.
Avoid fine, fluffy mulches for water saving — they mat down and shed water once dry.
Mulching in the right order
Weed first, apply soil wetter, water deeply, then mulch — in that order, in late spring. Keep mulch a hand-width clear of plant stems and trunks; piled against bark it holds moisture where plants least want it.