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Mulch Calculator for Beds, Borders and Topsoil
Mulch, topsoil or compost for any bed, at any depth.
Mulch and Soil Calculator tool
Circular beds.
If you already know it.
5 to 7.5 cm suppresses weeds; 10 cm or more for a new bed of topsoil.
Optional.
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Volume needed
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In litres
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Bags
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Bulk bags
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Approximate weight
| Measure | Value |
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Mulch settles, so order for the depth you want after settling: about ten per cent more than the bare calculation. Keep mulch clear of plant stems and tree trunks, where it holds moisture against the bark.
About the Mulch and Soil Calculator
Mulch and Soil Calculator turns a bed area and a depth into a volume, then into the bags and bulk bags garden centres actually sell. Mulch and topsoil are priced by volume in litres or cubic metres, and the gap between the two units is where most ordering mistakes happen: a cubic metre is a thousand litres, so twenty 50-litre bags make one cubic metre.
Depth is the input to get right. Five to seven and a half centimetres of mulch is enough to suppress weeds and hold moisture; less does not work, and much more can starve roots of air. A new bed of topsoil wants ten to fifteen centimetres, and a lawn top dressing only one or two.
The weight figure is there for a practical reason. Topsoil is nearly four times as heavy as bark mulch for the same volume, so a cubic metre of mulch is about 350 kg and a cubic metre of topsoil about 1,300. That is the difference between a wheelbarrow job and a day's work, and it is worth knowing before a bulk bag arrives at the kerb.
The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.
Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.
Looking for something this does not cover? FreeToolsZone.org is more free browser-based tools, organised by job, and it is worth a look if mulch and soil calculator is only part of what you are working on.
How to use the Mulch and Soil Calculator
- Choose bed shape and materialThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
- Enter length (m), width (m) and diameter (m)Decimals are fine, and thousands separators are accepted and ignored.
- Read the volume needed, in litres and bagsThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows volume needed, in litres, bags, bulk bags and approximate weight together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The mulch and soil calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Working out mulch for a border at the right depth
- Ordering topsoil for a new raised bed
- Converting between bags and bulk bags
- Checking the weight before a bulk delivery
Frequently asked questions
How deep should mulch be?
Five to seven and a half centimetres for weed suppression and moisture. Thinner does not work; much thicker can suffocate roots.
How many bags in a cubic metre?
Twenty 50-litre bags, since a cubic metre is a thousand litres. Bulk bags are usually around 0.8 cubic metres.
Why does the weight matter?
Because topsoil is about four times heavier than bark mulch per cubic metre. A bulk bag of soil is roughly a tonne, which affects how you move it.
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.