Mulch Calculator

How it is calculated

The bed is treated as a rectangle with a flat layer of mulch. Length and width are in metres, depth is in centimetres and the bag size is in litres. Volume is V = length × width × (depth ÷ 100) in m³, and litres are V × 1000. The number of bags is ⌈litres ÷ bag size⌉, rounded up to whole bags. All four values are required and must be above zero, and a depth above 100 cm gives no result because a layer deeper than a metre is not a garden bed. The volume is shown to two decimals, litres to whole numbers. There is no allowance for settling, irregular edges or plants and borders that take up space in the bed, so for a curved or uneven bed split it into rectangles, add them up and consider a few extra bags.

Common mistakes

• Entering the depth in metres or millimetres. The field is centimetres, so 0.07 gives a nearly empty bed, and 70 for a 7 cm layer gives ten times too much.
• Entering the bag size in cubic feet or gallons. The tool needs litres, so a 2 cubic foot bag, about 57 L, must be converted first.
• Measuring the bed in feet. Length and width are metres, so 13 for a 4 m bed gives a volume more than thirty times too large.
• Ignoring the rounding up. 8.4 bags means 9, and the extra 0.6 of a bag is useful for patching thin spots later.
• Applying one rectangle to a curved bed. Measure its average width or split it into several rectangles, otherwise the volume is off.