Gardening
Mulch Calculator
Enter bed area and mulch depth to see cubic volume and bags to buy.
How much mulch do I need?
Mulch volume is bed area × depth. Decorative bark often sits around 5–8 cm; weed-suppressing layers may need the deeper end of that range, while plant crowns must stay clear. Convert cubic volume to bags using the bag volume printed on the label (for example 50 L = 0.05 m³) and round up. Irregular beds and settling after the first rain mean a little extra is wise; for large areas, order loose cubic metres from a yard instead of dozens of bags. Top-dressing with compost uses similar volume maths but a different product — see the compost calculator — and for filling new beds compare garden soil.
Worked example
20 m² at 5 cm (0.05 m) depth = 1.0 m³. With 50 L bags (0.05 m³) that is 20 bags; at £5/bag ≈ £100.
Limits and assumptions
Loose volume before settling. Slopes, paths and densely planted beds change how evenly mulch spreads.
Frequently asked questions
How deep should mulch be for weed control?
Often toward 5–8 cm, keeping mulch off stems and crowns. Check guidance for the plants you are covering.
Bark mulch or compost — which tool?
Use this page for surface mulch volume; use the compost calculator when you are improving soil with compost.
When should I buy bulk instead of bags?
When cubic volume is large enough that bag counting becomes expensive — yards quote cubic metres directly.
Do I measure the whole garden?
Measure only the beds and paths you will actually mulch.