Mulch Calculator
Calculate exactly how much mulch you need for your garden beds, pathways, and landscaping projects. Get results in cubic metres, tonnes, and bags.
Calculate Your Mulch
Recommended depth: 50-100mm for garden beds
Total Volume
Volume: Length × Width × Depth (converted to metres). For circles: π × radius² × depth. For triangles: ½ × base × height × depth.
Weight: Volume × material density. Wood chip mulch has a density of 0.4 t/m³, while bark mulch is lighter at 0.35 t/m³.
Bags: Weight in tonnes × 50 (standard 20kg bags). We round up to ensure you have enough mulch.
Bulka Bags: Volume ÷ 1.0 (standard 1m³ bulka bag). Rounded up for ordering purposes.
How to Calculate Mulch for Your Garden
Calculating the right amount of mulch for your Australian garden is essential for achieving optimal plant health and minimising waste. Whether you're preparing garden beds, creating pathways, or landscaping a large area, our mulch calculator takes the guesswork out of your project planning.
Understanding Mulch Measurements
In Australia, mulch is typically sold by the cubic metre (m³). To calculate how much you need, you'll multiply your area's length by width by depth. Our calculator converts your measurements instantly and provides results in cubic metres, tonnes, and bag quantities, making it easy to order the exact amount you need.
Choosing the Right Mulch Depth
For most Australian garden beds, a depth of 75mm strikes the right balance between weed suppression and moisture retention. If you're mulching around annual flower beds or areas with established plants, 50mm is usually sufficient and allows delicate stems to breathe. For native gardens, steep slopes, or areas where maximum weed control is the priority, go deeper at 100mm. This thicker layer creates a more effective barrier against weeds while providing better insulation for plant roots during temperature extremes.
Types of Mulch Available in Australia
Wood chip mulch at 0.4 tonnes per cubic metre is the most popular all-purpose option, made from chipped tree branches and ideal for pathways where its chunky texture provides excellent longevity. Bark mulch is slightly lighter at 0.35 t/m³ and breaks down slower than wood chips, making it a favourite for formal gardens where appearance matters. Pine bark at 0.3 t/m³ is the lightest option and naturally acidic, which makes it perfect for acid-loving plants like azaleas, camellias, and many Australian natives.
Cypress mulch at 0.45 t/m³ offers natural resistance to termites and fungal decay, making it the smart choice for areas near buildings or in regions with high termite activity. Eucalyptus mulch weighs in at 0.4 t/m³ and carries the distinctive scent of native Australian bush while breaking down to improve your soil quality over time. For vegetable gardens, sugar cane mulch at just 0.2 t/m³ is extremely lightweight and breaks down quickly, adding valuable nutrients back into your soil with each growing season.
Hardwood mulch at 0.5 t/m³ is denser and longer-lasting, perfect for low-maintenance areas where you want mulch that will stay in place for years.
Tips for Applying Mulch
To get the best results from your mulch application, always keep mulch 50-100mm away from plant stems and tree trunks to prevent collar rot and fungal issues. Water the area thoroughly before spreading your mulch, then water again after application to help it settle into place. Since organic mulches break down over time, plan to top up your mulch layer annually to maintain effective coverage. For extra weed suppression in problem areas, consider laying newspaper or cardboard underneath your mulch before spreading—this creates an additional barrier that smothers existing weeds while eventually breaking down to feed your soil.
Ordering and Delivery
Once you've calculated your mulch requirements, you can order from your local landscape supplier. Most suppliers in Australia deliver in bulk by the cubic metre or in bags. For larger projects, bulk delivery is significantly more cost-effective, while bags are convenient for smaller jobs or areas with limited access where a truck can't reach.
Frequently Asked Questions
To calculate mulch volume, measure your garden bed's length and width in metres, then multiply by your desired depth (converted to metres). For a 5m x 3m bed at 75mm depth: 5 × 3 × 0.075 = 1.13 cubic metres. Use our calculator above to get instant results including weight and bag quantities.
In Australian gardens, mulch should typically be applied at 50-100mm depth. For weed suppression and moisture retention, 75mm is ideal for most garden beds. Around plants, keep mulch 50-100mm away from stems to prevent rot. In high-traffic areas or slopes, consider 100mm for better coverage.
A standard 6x4 trailer holds approximately 0.7-1 cubic metre of mulch when filled level. A tandem trailer (8x5) holds about 1.5-2 cubic metres. Remember that mulch is sold by volume (cubic metres) but may settle during transport, so slight variations are normal.
Wood chip mulch (0.4 t/m³) is chunky and long-lasting, ideal for paths. Bark mulch (0.35 t/m³) is finer and great for garden beds. Pine bark (0.3 t/m³) is lightweight and acidic, perfect for natives. Sugar cane mulch (0.2 t/m³) breaks down quickly, adding nutrients to soil. Choose based on your garden's needs and aesthetic preferences.
Multiply the volume in cubic metres by the mulch's density. Wood chip mulch has a density of approximately 0.4 tonnes per cubic metre, so 1m³ of wood chip weighs about 0.4 tonnes (400kg). Our calculator automatically converts between volume and weight for all mulch types.