Mulch Calculator
Calculate how many cubic yards or cubic metres of mulch you need for a garden bed, plus bags required.
Did this tool work for you?
How to use this calculator
Multiply the garden bed area by the desired mulch depth to get the volume. Convert to cubic yards by multiplying by 1.30795. Divide volume by bag size to get number of bags needed.
- 1
Measure your garden bed area in square metres.
- 2
Enter the desired mulch depth in centimetres (7–10 cm is typical).
- 3
Read off the volume in cubic metres and cubic yards.
- 4
Use the bag counts to purchase the right number of bags.
Frequently asked questions
What formula does the mulch calculator use?
Volume in cubic metres = bed area in m² × depth in cm ÷ 100. Cubic yards are the cubic-metre figure multiplied by 1.30795. Bag counts come from dividing the volume by the bag size and rounding up.
Which bag sizes does it count?
Two: 50 litre bags and 2 cubic foot bags. The 50 litre count is volume in litres ÷ 50, rounded up. The 2 cubic foot count converts yards to cubic feet at 27 per cubic yard, divides by 2 and rounds up.
Does it add extra for settling or waste?
No. The result is the exact volume for the area and depth you enter, with bag counts rounded up to whole bags. Add your own margin if you want spare material.
What depth should I enter?
The calculator has no recommended depth of its own. It defaults to 7.5 cm as a starting figure; enter whatever depth your supplier or garden plan calls for, in centimetres.
Why do the two bag counts differ?
A 2 cubic foot bag holds about 56.6 litres, which is more than a 50 litre bag, so fewer are needed for the same volume. At 7.5 cm over 10 m², the tool returns 15 of the 50 litre bags or 14 of the 2 cubic foot bags.
Is bulk delivery measured the same way?
The cubic metre and cubic yard figures are the ones to quote to a bulk supplier. Suppliers may sell by volume or weight, and bagged volumes printed on packs can differ slightly from the nominal size, so confirm with the label.
Can I use it for gravel, soil or compost?
The arithmetic is volume for any loose material spread at an even depth, so yes for quantity. It cannot convert to weight, since that depends on the material and its moisture.
Mulch volume and bag counts for a garden bed
Area times depth
Mulch is bought by volume, and volume is the footprint multiplied by the thickness you spread. The calculator takes the bed area in square metres and the depth in centimetres, converts the depth to metres and returns cubic metres. It then converts to cubic yards for suppliers who quote in them, and counts bags in two common sizes. The depth is the finished thickness after spreading, so a figure that is too thin or too thick scales the whole order directly. Because the depth field accepts decimals, you can compare options such as 5 cm and 7.5 cm side by side before choosing.
Conversions behind the output
The table sets out the unit relationships the code relies on when it turns a volume into bag counts.
| Quantity | Value used |
|---|---|
| 1 m³ in litres | 1,000 L |
| 1 m³ in cubic yards | 1.30795 yd³ |
| 1 yd³ in cubic feet | 27 ft³ |
| 50 L bag | Volume in litres ÷ 50, rounded up |
| 2 ft³ bag | Cubic yards × 27 ÷ 2, rounded up |
Worked results
The second table lists five bed sizes and depths with the volume and bag counts the calculator returned for each.
| Area and depth | Volume (m³) | Volume (yd³) | 50 L bags | 2 ft³ bags |
|---|---|---|---|---|
| 10 m² at 5 cm | 0.500 | 0.65 | 10 | 9 |
| 10 m² at 7.5 cm | 0.750 | 0.98 | 15 | 14 |
| 6 m² at 10 cm | 0.600 | 0.78 | 12 | 11 |
| 25 m² at 5 cm | 1.250 | 1.63 | 25 | 23 |
| 40 m² at 7.5 cm | 3.000 | 3.92 | 60 | 53 |
Reading the examples
The first two rows hold the area at 10 m² and change only the depth, and the volume and bag counts rise roughly in proportion to the depth. The third row is a small, deep bed at 10 cm. The final row, at 3.000 m², is the point where buying loose by the cubic metre or yard may start to make more sense than 60 bags, although prices, delivery fees and access decide that for you. Note that bag counts always round up, so the quantity bought slightly exceeds the volume needed.
Before you order
Measure the bed’s true area, using a garden bed area calculator for round or L-shaped beds, and subtract any areas taken up by paving, trees or plant crowns that you do not intend to cover. Check the printed bag volume, because bags sold by weight or by dry measure do not always match the nominal size. The result assumes an even, flat spread with no allowance for settling.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →