Mulch calculator: bulk m³ vs 50 L bags

How it works

Enter the bed area in square metres and the mulch depth you have chosen in millimetres. For separate beds, calculate each bed area and add the areas together if they will use the same depth.

The result converts the volume to litres and estimates how many 50 L bags to buy, rounded up to whole bags. The bag size is one sourced product example, mulch types and bag sizes vary between suppliers.

You may enter the bag price and/or bulk price per cubic metre. When both are entered, the comparison uses the whole bag count for bagged mulch and the exact estimated volume for bulk. It does not assume a minimum delivery, delivery charge, price discount or supplier order increment.

Formula

• Mulch volume (m³) = bed area (m²) × entered depth (mm) ÷ 1,000.

• Bag count = volume (litres) ÷ 50 L per bag, rounded up. Cost comparison uses whole bags × your bag price versus volume × your bulk price per m³.

Worked example

1. 1

   A 3 m × 3 m bed has an area of 3 × 3 = 9 m². At an entered depth of 100 mm (0.1 m), volume is 9 × 0.1 = 0.9 m³, or 900 L. At 50 L each, 900 ÷ 50 = 18 bags.

2. 2

   This is the volume at the depth you entered. It does not recommend how deep to mulch a particular plant bed.

Assumptions and limits

The bag estimate uses Pinegro Black Mulch, listed as 50 L. A litre rating is a volume label, not a weight, product type, moisture and settling can affect delivered quantity. The ABC gardening calculator supports the area × depth volume method.

The result does not include extra for settling, uneven ground, edges, slopes, existing mulch or delivery. Bulk mulch prices are compared at the exact calculated volume even if a supplier has a minimum order, contact the supplier to confirm the delivered quantity and price.

Measure the area and use a depth selected for your plants and site. The tool estimates materials only and does not assess plant health, soil condition, fire risk, drainage or local restrictions. Ask a qualified local horticultural professional if you need advice for a particular planting.

Frequently asked questions