1. What are you spreading?
Not sure how deep? Mulch 50–75 mm suppresses weeds; lawn soil ~100 mm; veggie beds 300 mm+; gravel 50–100 mm.
2. Measure the area
Add one area for each bed or section. Enter metres — we convert to m² and then m³.
3. Bags & cost (optional)
There are 1,000 litres in a cubic metre, so one m³ ≈ forty 25-litre bags.
How to work out how much soil, mulch or gravel you need
Where turf is measured in square metres, loose materials like soil, mulch and gravel are measured by volume — in cubic metres (m³). The maths is one extra step: work out the area you're covering, then multiply by how deep you want the material to sit.
A 24 m² garden bed at 75 mm (0.075 m) of mulch needs 24 × 0.075 = 1.8 m³.
The calculator does this for you: pick your material (which sets a sensible depth you can adjust), add each area, and it returns the cubic metres plus how that converts into bags or bulk bags.
Recommended depths
| Material / use | Typical depth |
|---|---|
| Garden mulch (weed suppression) | 50–75 mm |
| Lawn underlay soil (before turf) | ~100 mm |
| New vegetable garden bed | 300 mm+ |
| Decorative gravel / pebble | 50–75 mm |
| Gravel driveway | ~100 mm |
Bags or bulk?
As a rough guide, once you're past about half a cubic metre, a bulk delivery usually works out cheaper and saves lugging dozens of bags. Below that, bagged material is convenient and easy to store. The calculator shows both so you can compare — there are 1,000 litres in a cubic metre, so a single m³ is roughly forty 25-litre bags.
Soil, mulch & gravel FAQ
How much mulch do I need for my garden?
Measure each bed's area in square metres, then multiply by your mulch depth in metres (75 mm = 0.075 m). Add the beds together for your total in cubic metres. Enter your measurements above for an exact figure and a bag count.
How many bags of soil are in a cubic metre?
It depends on the bag size. With common 25-litre bags, one cubic metre is about 40 bags (1,000 ÷ 25). Set your bag size in the calculator and it works out the number for you.
Should I order extra?
Yes — a little. Mulch and soil settle, and it's easy to underestimate depth over an uneven bed. Ordering 5–10% extra means you finish the job and have a bit spare for topping up later.