Garden materials calculator
Enter the size of an area and how deep you want the layer, and the calculator shows how much mulch, bark, compost, topsoil or gravel to order, in volume and in bags. A second calculator counts the paving slabs for an area, with extra for cuts and breakage.
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Mulch, bark, compost, topsoil or gravel
0.6 m³ (600 litres) for 8 m² at 7.5 cm deep.
That is 12 bags of 50 litres, rounded up.
Paving slabs
28 slabs for 9 m²: 25 to cover the area, plus 10% extra, rounded up.
How the numbers are worked out
- Volume = length × width × depth. In metric, the depth in centimetres is divided by 100, and 1 m³ is 1,000 litres. In imperial, the depth in inches is divided by 12, and 1 cubic yard is 27 cubic feet.
- Bags = volume ÷ bag size, rounded up to a whole bag.
- Slabs = area ÷ the area of one slab, plus the extra percentage, rounded up. Joints between slabs aren't counted, so the result is on the safe side.
Tips for measuring
- Split an irregular bed into rectangles, work each one out, and add the results.
- Check the bag size printed on the bag before you compare prices: bags of the same product come in different sizes.
- For mulch, the RHS advises a layer at least 5 cm (2 in) deep, ideally 7.5 cm (3 in), and keeping a 10 cm (4 in) circle around woody stems free of mulch. See the RHS guide to mulches and mulching.
- Round up when you order. Running short halfway through a bed costs a second delivery.
From a garden design to a shopping list
A design picture has no measurements, so the numbers have to come from a tape measure. If you have tried ideas on a photo of your garden in the AI garden design app, measure the beds, paths and patio in the design you chose, then use the calculators above for each one.