Calculate how much mulch, compost, or topsoil you need for garden beds — in cubic metres/litres (metric) or cubic yards/cubic feet (US), with bag counts and cost.
Add each garden bed's length and width below and pick your units — the calculator totals the area, applies your mulch depth, and gives volume, bag counts and cost whether you buy by the cubic metre (AU) or the cubic yard (US).
Add multiple beds or areas to calculate the total.
| Item | Value |
|---|
Mulch is essential in Australian gardens to retain moisture, suppress weeds, regulate soil temperature, and improve soil health. During hot Australian summers, a 75–100mm layer of mulch can reduce watering frequency significantly.
| Application | Depth |
|---|---|
| Garden beds (general) | 75–100mm |
| Trees and large shrubs | 100–150mm |
| Vegetable gardens | 50–75mm (pea straw/sugar cane) |
| Top-up (existing mulch) | 25–50mm |
Mulch is sold in 30L or 60L bags at Bunnings/Mitre 10, or by the cubic metre via landscape suppliers. Bulka bags (1m³) are economical for medium jobs. Trailer loads (1–3m³) suit larger projects. Always buy 10% extra for settling.
| Depth | Coverage per m³ | Use |
|---|---|---|
| 50 mm (2 inches) | 20 m² | Top-up existing beds |
| 75 mm (3 inches) | 13.3 m² | New beds, weed suppression |
| 100 mm (4 inches) | 10 m² | Heavy weed suppression |
| Mulch Type | Best For | Lifespan |
|---|---|---|
| Pine bark (coarse) | Garden beds, shrubs | 2-3 years |
| Sugar cane mulch | Vegetable gardens, fast breakdown | 6-12 months |
| Lucerne (alfalfa) / straw | Vegetables, nitrogen-rich | 3-6 months |
| Eucalyptus / hardwood woodchip | Native gardens, paths | 3-5 years |
| Dyed mulch (red, black, brown) | Decorative colour, US front yards | 1-2 years (colour fades faster) |
| Pebble / gravel mulch | Low-maintenance, permanent | Indefinite |
Mulch is bought differently in each market. Australian nurseries and landscape suppliers sell mulch by the cubic metre (m³) in bulk, or in 30L/60L bags for small jobs. US garden centres sell mulch mostly in 2 cubic-foot bags, with bulk deliveries priced by the cubic yard. Use the Metric/US toggle above the calculator to switch instantly.
| Measure | Australia / Metric | United States |
|---|---|---|
| Bulk volume unit | Cubic metre (m³) | Cubic yard (cu yd) |
| Common bag size | 30L or 60L | 2 cu ft (≈56.6 L) |
| Bags per bulk unit | ~16-33 bags per m³ | ~13.5 × 2 cu ft bags per cu yd |
| Conversion | 1 m³ = 1.308 cu yd | 1 cu yd = 27 cu ft = 0.765 m³ |
How much mulch do I need for my garden?
Measure the area of each garden bed (length × width) and add them together, then multiply by your target depth. 1 m³ covers approximately 13-14 m² at 75mm (3in) depth — the recommended depth for effective weed suppression. This calculator totals multiple beds and works in either metric or US units.
How many cubic feet are in a yard of mulch?
One cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). Since most US mulch bags hold 2 cubic feet, one cubic yard of bulk mulch is roughly equivalent to 13-14 bags — which is why bulk delivery is usually far more economical for anything beyond a small bed.
What depth should I apply mulch?
For weed suppression, aim for 75mm (3 inches) minimum. For top-up maintenance, 25-50mm (1-2 inches) is enough. The most important rule: never pile mulch against plant stems or tree trunks — leave a clear gap. "Volcano mulching" (piling against trunks) traps moisture, causes disease, and can eventually kill trees.
How do I figure out how much mulch I need?
Multiply the garden bed area by the depth of mulch you want, in either metric or US units. A common depth is 50-75 mm (2-3 in). This mulch calculator does the maths — enter each bed's length and width plus your depth, and it totals the volume, bags and cost needed.
What mulch colour should I choose?
Dyed mulch (red, black or brown) is popular in the US for consistent colour year-round, though the dye fades over 1-2 years and needs topping up. Natural bark and woodchip mulches (common in Australia) weather to a neutral grey-brown but break down into the soil, improving it over time.
How much mulch is in a bulk delivery load?
A standard bulka bag (AU) holds about 1 m³, while a typical bulk mulch delivery truck (US) drops a set number of cubic yards you order in advance. Both are far cheaper per unit volume than buying bags for anything larger than one or two garden beds.