This calculator works out how much mulch, bark or compost you need to cover a garden bed. Enter the bed dimensions and the depth of the layer and it returns the volume to buy — in cubic metres, or cubic feet and cubic yards in imperial mode.
How it works
The volume is the bed area multiplied by the layer depth, with the depth converted into the same unit as length:
volume = length × width × depth
In metric mode depth is entered in millimetres and divided by 1000 to metres; in imperial mode depth is in inches and divided by 12 to feet. Imperial results are also shown in cubic yards (volume ÷ 27), since suppliers commonly sell by the yard. A 50–75 mm (2–3 inch) layer is recommended for weed suppression and moisture retention.
Example
A 5 m × 2 m bed with a 50 mm mulch layer:
area = 5 × 2 = 10 m²; depth = 50 ÷ 1000 = 0.05 m; volume = 10 × 0.05 = 0.5 m³.
| Bed size | Depth | Volume |
|---|---|---|
| 5 m × 2 m | 50 mm | 0.5 m³ |
| 5 m × 2 m | 75 mm | 0.75 m³ |
| 10 ft × 4 ft | 3 in | 10 ft³ (≈0.37 yd³) |
All calculations run entirely in your browser and nothing is sent to a server.