What this calculator works out
This calculator converts an area and a depth into a volume of bark chippings in litres, with an allowance for uneven spreading.
The arithmetic is identical to the mulch calculator — bulk material is bulk material. What differs is the depth appropriate to bark and what it is used for.
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Before you order
- 5 cm is a reasonable depth for beds and borders. Paths and play areas need considerably more, often 10 to 15 cm, because bark compacts underfoot.
- Bark grades vary. Fine composted bark suits beds; coarse chips last longer and suit paths.
- Play-grade bark is a specific product tested for impact absorption, and general landscaping bark is not a substitute for it.
- Bark decomposes and needs topping up — typically every two to three years on a bed.
Composted bark has been stacked and partially decomposed, so it is darker, finer and stable in a bed. Fresh chipped material is lighter, coarser and still breaking down, which makes it better for paths and worse next to plants. Suppliers use the terms loosely, so check what you are buying.
How this calculator works
Area times depth, converted to litres:
Litres = area × depth × 10 × (1 + allowance ÷ 100)Bark settles more than compost does, particularly on a path where it is walked on. For a path, ordering the calculated volume and expecting to top up after the first season is realistic.
Worked example: a 20 m² area
Using the default figures — 20 m² at 5 cm deep with a 10% allowance:
- Base volume: 20 × 5 × 10 = 1,000 litres
- With allowance: 1,100 litres
1,100 litres covers a 20 m² border comfortably. The same area as a path at 10 cm needs 2,200 litres — double, and it will still compact down over the first year. Bark paths are cheap to lay and are a recurring cost rather than a one-off.
Common mistakes
- Using bed depths for a path. Paths compact and need twice as much.
- Using landscaping bark under play equipment. Play-grade bark is a tested product.
- Laying bark over weeds. Clear perennial weeds first; bark suppresses seedlings only.
- Piling it against stems. Keep a clear zone around each plant.
- Expecting it to last indefinitely. It breaks down and needs topping up.
Frequently asked questions
How long does bark mulch last?
On a bed, typically two to three years before it needs topping up, depending on the grade and the climate. Coarser chips last longer than fine composted bark. On a path it compacts within a season and is usually topped up annually.
Should I use a membrane under bark?
Under a path, yes — it keeps the bark separate from the soil and stops it working down into the ground. Under a planted bed, generally no: membrane prevents organic matter reaching the soil, roots grow through it, and it eventually breaks into fragments that are difficult to remove.
Is bark safe around pets and children?
Ordinary landscaping bark is not toxic, though some dogs chew it and can suffer digestive obstruction. Cocoa shell mulch is a genuine hazard to dogs and should be avoided in gardens they use. For play areas, use bark specifically graded and tested for impact absorption.
Does bark make soil acidic?
Only marginally, and mostly in the thin layer where it meets the soil. The effect on established plants is negligible. The common advice to use bark specifically for acid-loving plants overstates a very small effect — ericaceous compost is the appropriate product for those.
Is what I enter stored?
No. Measurements are processed in your browser and never transmitted or retained.
Related tools
References
- Royal Horticultural Society — mulching materials, depths and plant safety
- GOV.UK — playground surfacing standards and garden product safety
Sources are checked at publication and can change — how I choose and check references.