Mulch Calculator guide
Mulch Calculator: How Much Bark or Compost Do I Need?
Use our mulch calculator to work out how much mulch, bark chippings or compost you need for a garden bed, in litres, cubic metres and bags.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
A layer of mulch keeps weeds down, holds moisture in the soil and makes beds look tidy. Our Mulch Calculator works out how much to buy.
How to use the calculator (Mulch Calculator)
- Enter the length and width of the bed.
- Enter the depth of mulch you want.
- Enter the bag size in litres and, optionally, the price per bag.
How it works
Volume = length × width × depth
1m³ = 1,000 litres, so a 60-litre bag covers about 1.2m² at a depth of 5cm.
How deep should mulch be?
| Use | Depth |
|---|---|
| Garden compost or manure | 5–8cm |
| Bark chippings | 5–8cm |
| Gravel mulch | 2–5cm |
The RHS recommends at least 5cm to suppress weeds.
A worked example
With the calculator's default settings, a 5m × 2m bed with a 5cm layer needs 0.5m³, which is 500 litres, or 9 60-litre bags.
Frequently asked questions
When should I mulch?
In late winter or spring, when the soil is moist but not frozen, or in autumn.
Should mulch touch plant stems?
No. Leave a gap of a few centimetres around stems and tree trunks to prevent rotting.
Is a bulk bag cheaper?
Often, for big areas. Bulk bags are usually around 0.7 to 1m³, so check with your supplier.
For gravel and aggregates, use our Aggregate Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.