Mulch calculator
Work out how much bark or wood-chip mulch you need for a bed or border, or — if you already have a set number of bags — how far they'll stretch.
Result
Mulch required
Bags needed (50L)
Result
Length you can cover
How to use this tool
- Measure the area you're mulching.
- Enter the depth you intend to apply. Mulch type, planting and purpose affect suitable depth; use product or trusted horticultural guidance.
- Read the volume required and the equivalent number of bags, or use reverse mode if you already have bags on hand.
Assumptions
- Entered area × depth gives the geometric volume before the editable allowance. Bag count assumes 50L per bag and rounds up; it is exact only if the product volume matches that assumption. Check the package volume.
- The calculation does not predict settling, decomposition or an appropriate application depth for the selected mulch and plants.
Technical details: what the fields mean
- Length
length - The longest side of the area to mulch.
- Width
width - The other side of the area to mulch.
- Depth
depth - Chosen layer thickness. The calculator converts this depth into volume; there is no single depth suitable for every mulch and planting situation.
- Waste allowance
wastePercent - Optional editable allowance for uneven ground or settling; the default is illustrative.
Methodology
Volume = length × width × depth, increased by the waste allowance. Bags assume a standard 50L bag.
Worked example
5m × 2m border, 6cm mulch, 10% waste
Inputs: Length: 5 m, Width: 2 m, Depth: 6 cm, Waste allowance: 10%
Result: 0.66 m³ required, 14 bags
Practical guidance
- Keep mulch a few centimetres clear of plant stems and tree trunks to avoid rot.
- Wood-chip mulch is cheaper and better for paths; bark mulch looks tidier in ornamental beds.
Common mistakes
- Piling mulch directly against stems and trunks ('mulch volcanoes'), which encourages rot and pests.
- Under-ordering because settling over the season isn't accounted for.
FAQs
How deep should garden mulch be?
It depends on mulch type, plants and purpose. Choose a depth based on product instructions or appropriate horticultural guidance; this calculator only converts your chosen depth to volume.
I have a fixed number of bags — how far will they go?
Use reverse mode below: enter your bag count, width and depth to see the length you can cover.
Last reviewed: 2026-10-11
A simple rectangular-area estimate — an irregular bed shape needs a rough area equivalent instead.
This tool provides an indicative estimate, based on the assumptions stated above.
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