How much mulch do I need?

Multiply the garden area by the depth of mulch to get the volume in cubic metres, then divide by the bag size if you are buying bags. The calculator does both. Bagged mulch is often sold in 40 to 60 litre bags.

How deep should mulch be?

A layer of about 50 to 75 mm is usual for suppressing weeds and holding moisture, kept clear of plant stems. Thinner layers break down and need topping up sooner. Enter your chosen depth in millimetres.

How many litres in a cubic metre?

There are 1,000 litres in a cubic metre. So a 50 litre bag is 0.05 of a cubic metre, and it takes 20 of those bags to make one cubic metre. Bulk mulch by the cubic metre is usually cheaper for large areas.

Mulch Calculator

This calculator works out how much mulch or bark you need to cover a garden bed, so you can order the right amount instead of guessing and running short or paying for surplus. You enter the garden area in square metres, the depth of mulch you want in millimetres, and the bag size in litres if you plan to buy bagged mulch rather than bulk. It multiplies the area by the depth to get the volume in cubic metres, converts that to litres, then divides by your chosen bag size to show how many bags to buy, rounding up so you never fall short. The results update instantly as you type: the total volume needed in cubic metres, the number of bags at your chosen size, and the equivalent volume in litres. Most gardens are mulched to a depth of 50 to 75 mm, deep enough to suppress weeds and hold moisture without smothering plants, so try that range if you are unsure. For larger areas, ordering mulch in bulk by the cubic metre is usually cheaper than buying many small bags, so use the cubic metre figure to compare bulk pricing against the bagged cost. Bag sizes and mulch density vary between suppliers, and settling over time can slightly reduce coverage, so treat the result as a solid guide and round up a little when ordering.

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Garden area (m²)

Depth (mm)

Bag size (litres)

0 m³

mulch needed

Bags0

Litres0 L

How it works

The volume is the area times the depth in metres. There are 1,000 litres in a cubic metre, so the calculator converts the volume to litres and divides by the bag size to get the number of bags, rounded up.

Worked example

For 15 square metres at 60 mm deep, the volume is 0.9 cubic metres, which is 900 litres. In 50 litre bags that is 18 bags, or you could order just under a cubic metre in bulk.

Related calculators

Topsoil Calculator: soil for a garden.
Gravel Calculator: gravel and aggregate.
Cubic Metre Calculator: work out a volume.
Square Metre Calculator: work out an area.

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