Mulch Calculator

Mulch is a volume problem

Bark and wood-chip products are commonly sold by bag or cubic volume. Weight is much less useful because moisture and material type vary so widely. The calculator therefore focuses on the space you want to cover and the package volume you can actually buy.

Worked example

Refresh layer versus new-bed depth

A bed that already has mulch usually needs only the extra depth you want to restore, not the full original layer. Measure the added depth. For a new bed, use the intended finished depth after spreading. Keeping those two cases separate can prevent major over-ordering.

Bulk versus bagged mulch

Bag size in both unit systems

Metric mode accepts the bag volume in litres. Imperial mode accepts cubic feet; switching units converts a bag size already entered. For example, a 2 ft³ bag holds about 56.6 litres. The bag count always rounds up to a whole bag, while the bulk estimate uses cubic metres or cubic yards.

Curved and irregular beds

Divide complex beds into smaller rectangles or use several average-width sections. Avoid using one large surrounding rectangle when much of it is actually lawn or paving. Measuring several smaller zones is usually more accurate than adding a large safety percentage afterward.

Before ordering mulch

• Measure only the new depth you plan to add.
• Use the exact bag size printed on the product.
• Keep mulch away from direct contact with trunks and stems.
• Compare bagged and bulk quantities using the same volume basis.
• Treat decorative stone as gravel rather than organic mulch.

How to estimate a bed with plants

Measure the bed's planted surface, not a rectangle that includes adjacent paths. For several beds, calculate each volume separately and add them. If a circular bed has radius 1 m, its area is about 3.14 m²; at 5 cm new depth it needs roughly 157 litres before any top-up reserve. Keep mulch clear of the plant crowns and trunks when spreading.

Frequently asked questions