MetraNestDefine the area to cover
Measure the rectangles making up your garden bed and add their areas. Subtract any significant areas that will not receive mulch. For an L-shaped area, the area calculator avoids double counting. A curved border needs a suitable geometric estimate.
Layer depth is a project input
A one-centimetre difference may represent several bags over a large area. The right depth depends on the material and use; follow the chosen product’s instructions. The calculation does not choose the mulch type or assume that one depth suits every situation.
Understand the purchased surplus
The total volume is divided by the litres in one bag, then rounded up. The difference is the reserve provided by the last bag. If you want an extra reserve for settling or touch-ups, identify it separately. Do not add several allowances without knowing what each covers.
Volume in litres = area in m² × depth in cm × 10. Bags = required volume ÷ litres per bag, rounded up.
A small garden bed
For an area of 8 m² and a chosen depth of 5 cm, the volume is 8 × 5 × 10 = 400 L. With 50 L bags, that means eight bags. Increasing the depth to 6 cm would give 480 L, requiring ten 50 L bags.
Details to check
- Check the exact bag capacity.
- Keep the measured area and chosen depth as separate inputs.
- Combine several areas only if they use the same material and layer depth.
Frequently asked questions
Can I use this tool for a layer of decorative gravel?
The volume formula works for a uniform layer. If the product is sold by weight, you need its density; this tool does not guess it.
Should I add an allowance?
That depends on the material and measurement accuracy. Rounding up to whole bags already creates a reserve, which the result helps you identify.
Method and references · Editorial review: 25 October 2026
The geometric formulas are explained here. For a product, its packaging dimensions and coverage rate remain the reference inputs.