← 🏠 Homeowners and DIYers toolkit
Mulch and Topsoil Calculator
How much to order for a garden bed, border, lawn repair or raised bed.
Part of the 🏠 Homeowners and DIYers toolkit, with more tools made for the job.
Use this instead of length and width.
Leave empty for none.
Gives the number of bags.
Type the size and depth, and the volume you need appears here.
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Enter the size of the bed and how deep you want the layer. This shows the volume of mulch, topsoil or compost you need, in cubic metres and cubic yards, and the number of bags.
Garden materials are sold by the bag, the cubic metre or the cubic yard, and a thin layer over a big area adds up fast. The sum is area times depth, but with the depth in centimetres or inches and the area in metres or feet, so the units are easy to get wrong. For imperial users, area in square feet times depth in inches divided by 324 gives cubic yards, which is where that number comes from.
How it’s worked out
- Area is length times width, or the area you type directly.
- Volume is the area times the depth, with the depth converted to the same unit.
- An extra allowance is added if you want one, for settling and uneven ground.
- Bags are the volume in litres (or cubic feet) divided by the size of one bag, rounded up.
A 5 m by 2 m bed with 7 cm of mulch is 0.7 cubic metres. In 50 litre bags that is 14 bags. For a 10 ft by 8 ft bed 3 inches deep it is about 0.74 cubic yards.
Common mistakes
- Mixing inches with square feet or centimetres with square metres. Convert depth to match, or use the tool.
- Piling mulch against stems and trunks. It holds moisture and can rot the plant, so keep it back.
- Ordering topsoil without allowing for settling. Fresh soil compacts, so a little extra is sensible.
- Using one depth for everything. Mulch, topsoil and compost layers are different depths, and the tool lets you change it.
Questions
How deep should mulch be?
Advice differs by material and plant. Extension services often suggest a few centimetres or about 2 to 3 inches of organic mulch, kept away from stems. Check the advice for your plants.
How much does a cubic yard cover?
It depends on the depth. As a rule of thumb, one cubic yard covers about 100 square feet at 3 inches or about 324 square feet at 1 inch.
Does it work for compost, gravel or sand?
Yes. Any loose material laid to a depth works the same. Weight depends on the material, so ask your supplier how much a cubic metre weighs.
How do I measure an odd-shaped bed?
Split it into rectangles and circles, work out each area, and add them. The area box takes the total.
Where the method comes from
Estimates only
These are estimates and general information, not building, safety, legal or professional advice. Materials, coverage, waste and rules vary by product, project and place, so check the maker's instructions and your local rules, and use a qualified person for gas, electrical and structural work.
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