Bark Calculator

Work Out How Much Bark You Need

How the Calculation Works

The calculator multiplies your area in square metres by the depth you choose, converted to metres, to get a volume in cubic metres. One cubic metre is exactly 1,000 litres, so that volume converts directly to litres — the unit UK bagged and bulk-bagged bark is sold in. If you enter an extra allowance, it is applied to the volume first. The number of packs is then the litres needed divided by the pack size you chose, and the result is rounded up to a whole pack, because part-packs are not sold. Both the exact figure and the rounded-up figure are shown, so the rounding is visible rather than hidden. The coverage figures here are arithmetic — they follow from the area and the depth you enter and need no outside authority. How deep to spread bark is a different kind of question: that is horticultural guidance, and it is drawn from the sources listed below. Manufacturer coverage claims are never used as the calculator formula, because a coverage figure like "one bulk bag covers so many square metres at a stated depth" is itself just this same arithmetic run in reverse for one particular product.

Measuring Your Area

For a rectangular or square bed, measure the length and width in metres. For a round bed, measure straight across the widest point — the diameter — in metres. If you already know the area, you can enter it directly in square metres instead. An irregular bed can be measured by splitting it into simpler rectangles and circles, working out each part separately, and adding the areas together before you enter a total. This section is about measuring only — how deep to spread the bark once you know your area is covered separately below.

How Deep to Spread Bark

The Royal Horticultural Society says biodegradable mulches need to be at least 5 cm thick, and ideally 7.5 cm thick. That is a minimum plus an ideal, not a single figure, and it covers biodegradable mulches generally rather than bark specifically.

Leeds City Council's own landscape planting specification requires bark mulch to a depth of 75 mm on shrub, herbaceous and hedging planting in schemes submitted for planning approval. That is a municipal planning requirement binding on applicants in Leeds, not general garden guidance for the rest of the country — though it does corroborate the RHS's 7.5 cm figure from a different kind of authority.

Individual UK bark suppliers give their own application instructions, and these differ by product: Melcourt and AHS both instruct 50 to 100 mm depending on the product, while Rolawn instructs 50 mm. These are manufacturer application instructions for their own products, not horticultural recommendations, and they should not be read as one agreed norm.

The RHS also advises against piling mulch against the stems of woody plants, and against letting it smother low-growing plants. A single tree or specimen shrub is best mulched out to the radius of its canopy.

Bags and Bulk Bags: What Sizes Actually Exist

There is no standard UK bark bag size. Bagged bark is sold in a range of volumes — 60 litre bags from Melcourt and Hallstone, 70 litre bags from Premium Topsoil Supplies, and 100 litre bags from Wickes. Bulk bags vary even more: 500 litres from Hallstone and Rolawn, 750 litres as Rolawn's larger option, 1,000 litres from AHS, and Premium Topsoil Supplies alone offers 700, 1,000 and 1,200 litre bulk bags — three different volumes from a single supplier. That is the clearest evidence that bulk-bag size has to be read off the actual product rather than assumed, which is why this calculator asks for the litres your bag or bulk bag actually holds, with these observed sizes offered as a shortcut rather than a default. Melcourt also states that its bark products undergo 5 to 10 percent natural settlement — a statement about Melcourt's own products, not a UK-wide figure, and it is never applied automatically here. Bark is a natural product, and Melcourt notes that quoted values can vary. If you want to allow for settlement, topping up, or an uneven bed, use the extra-allowance field below and choose your own figure.

A Worked Example

Both examples below use the calculator's own arithmetic. Each pack size shown is an example of a real UK pack size, never a standard one — and where an extra allowance appears, it is that example's own chosen figure, not a recommendation.

Play Bark: Quantity Only

If you select play bark, the volume calculation is exactly the same arithmetic as for any other bark — your area multiplied by whichever depth you enter. Selecting play bark changes no default, no depth and no output; it exists only so the calculator recognises the product you're buying. How deep play bark needs to be for safety surfacing is a separate question, governed by its own testing standards, and this page does not answer it — it works out volume only.

What This Calculator Doesn't Cover

This calculator gives volume rather than weight, because declared UK bark densities differ materially by product: Melcourt states 200 to 250 kilograms per cubic metre for its 5 to 35 mm particle product, while AHS states typically 250 to 400 for its 10 to 60 mm particle product. With that much spread between two manufacturers, a single weight figure would carry more uncertainty than it would resolve. This page also does not cover prices, does not recommend a supplier, does not set a playground safety depth, does not give planting advice, and does not cover wood chippings.

Sources

These two sources provide horticultural and planning guidance on depth and placement, and are cited for that role only.

External source links open in a new tab.

• Royal Horticultural Society (RHS) — Mulch depth and placement guidance
• Leeds City Council — Landscape planting specification

These two sources provide product data — bag and bulk-bag sizes, settlement, and bulk density — and are cited for that role only; neither is used as horticultural authority.

• Melcourt Industries — Bagged bark product specification
• Wickes — Bagged bark product listing