Mulch calculator
Enter the size of your bed and how deep you want the mulch. You’ll get cubic metres for a bulk delivery and a bag count for the garden centre.
Measuring in feet and inches? Use the US version
Mulch needed
0.9 cubic metres (m³)
- Bags to buy
- 18 50 litre bags
- Litres
- 900 L
- Area covered
- 18 m²
How it works
Mulch is sold by volume. The calculator multiplies length × width (in metres) by depth (centimetres ÷ 100) to get cubic metres. Each cubic metre is 1,000 litres, so the bag count is litres divided by the bag size, rounded up.
For a curved or odd-shaped bed, split it into rough rectangles, work out each one and add them together.
Example
With bed length 6 m, bed width 3 m, mulch depth 5 cm, bag size: 50 litre bag, the answer is 0.9 cubic metres (m³).
Tips before you buy
- Keep mulch a few centimetres back from tree trunks and plant stems, where trapped moisture can cause rot.
- Topping up last year’s mulch usually needs only 2–3 cm. Check what’s already there before you order.
- Bulk bags and loose deliveries are usually cheaper than small bags once you need about a cubic metre.
Common questions
How many bags of mulch do I need per square metre?
At 5 cm deep, one square metre takes 50 litres, which is one 50 litre bag.
How much area does a cubic metre of mulch cover?
About 20 m² at 5 cm deep, or about 13 m² at 7.5 cm.
How deep should mulch be?
Most beds do well with 5 to 7.5 cm. Thinner layers let weeds through, and much more than 10 cm can stop water reaching the soil.