How Much Mulch Do I Need?

Depth first, area second

The biggest mulch mistake is depth, not area. Too thin and weeds push through within weeks; too thick and rain struggles to reach the roots. For most Australian garden beds, 75–100 mm is the sweet spot.

• General garden beds: 75–100 mm
• Native and drought-sensitive plants: around 50 mm
• Around tree trunks and house walls: keep mulch 10–15 cm clear of the surface itself
• Paths (chunky wood chip): 100 mm is comfortable to walk on

From bed size to cubic metres

Multiply length × width × depth (in metres). A bed 6 m × 2 m at 75 mm needs 6 × 2 × 0.075 = 0.9 m³. That's it — one number to take to the landscape yard.

For odd-shaped beds, break them into rectangles and add the volumes. Round up to the nearest 0.1 m³ when ordering bulk.

Bulk vs bagged

One cubic metre is 1,000 litres — twenty 50 L bags. Bagged mulch from the nursery is convenient for small beds but costs several times more per cubic metre than a bulk delivery. As a rule of thumb: over about 1 m³, bulk delivery wins on price if you have driveway space for the pile.

Expect it to settle

Fine mulches like sugarcane compact noticeably over a season; chunky barks hold their depth longer. Plan a top-up every 12 months or so rather than over-ordering on the first pass.