Mulch Calculator: measuring notes and method
Exclude non-mulched areas
Measure the actual bed area and intended mulch depth. Keep paths and clear areas out of the footprint rather than applying mulch to the entire garden rectangle.
Compare bags with bulk delivery
For bagged mulch, convert the required cubic metres to litres, divide by bag volume and round up. A volume-only order does not need a density conversion.
CHECK A PRACTICAL EXAMPLE
Compare the measured layer depths
A 5 × 4 m garden bed has no excluded area in this example. Density is held at an illustrative 400 kg/m³, with no allowance.
50 mm layer
- Material weight
- 400 kg
- Volume to order
- 1 m³
75 mm layer
- Material weight
- 600 kg
- Volume to order
- 1.5 m³
These are arithmetic options, not planting recommendations. For a volume-based order, use cubic metres; the weight estimate depends on the actual product density.
Fixed comparison in metric units. Values are illustrative unless linked to a recorded project; changing the calculator above does not change this example.
Formula
Volume = length × width × depth × (1 + waste ÷ 100). Mass = volume × density.
Worked examples in metric and imperial units
Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.
Metric worked example
- Length
- 6 m
- Width
- 4 m
- Finished depth
- 75 mm
- Bulk density
- 400 kg/m³
- Waste allowance
- 10 %
Material weight: 792 kg
Imperial worked example
- Length
- 19.685 ft
- Width
- 13.1234 ft
- Finished depth
- 2.9528 in
- Bulk density
- 24.9712 lb/ft³
- Waste allowance
- 10 %
Material weight: 1,746.0611 lb
Follow the calculation
Lengths in this working are in metres.
- Net volume = 6 × 4 × 0.075 = 1.8 m³.
- Allowance multiplier = 1 + 10 ÷ 100 = 1.1.
- Mass = 1.98 m³ × 400 kg/m³ = 792 kg.
Unit conversions
1 m³ = 1,000 L ≈ 1.30795 yd³. One cubic yard is 27 ft³.
For metric tonnes, divide kg by 1,000. For US short tons, divide lb by 2,000; a long ton is 2,240 lb. Confirm your supplier’s unit.
Reviewed 19 October 2026. How calculations are checked · Report a correction