Understand the estimate
Formula and assumptions
Volume = area × depth. Each bed is converted to cubic feet or cubic metres, then waste/settling is applied. Bags and bulk quantities are rounded up to purchasable units.
Volume = area × depth. Each bed is converted to cubic feet or cubic metres, then waste/settling is applied. Bags and bulk quantities are rounded up to purchasable units.
Assumptions to confirm
- Depth is the installed depth before long-term settling.
- Bag volume is the nominal label volume.
- Bulk delivery minimums and weight limits are not included.
- Gravel density varies, so tonnes are an optional planning conversion only.
Label every measurement and keep exclusions visible. Add the shapes in the calculator instead of hiding them inside one total.
Worked example
Input
A 20 × 6 ft bed at 3 in depth with 10% contingency and 2 cu ft bags.
Planning result
The plan needs 33 cu ft, or 17 bags. That is about 1.23 cubic yards before supplier minimums.
Common package sizes
Package conventions vary by brand and region. Enter the usable coverage or yield shown on the actual product instead of relying on the name or weight alone.
- 1–2 cu ft mulch or soil bags
- 25–50 L metric bags
- Bulk cubic-yard or cubic-metre delivery
Frequently asked questions
How deep should mulch be?
Two to four inches is common, but plant type, existing material, and drainage matter. Avoid piling mulch against trunks or foundations.
Why compare bags with bulk?
The lowest sticker price is not always cheapest per installed volume. Delivery charges and minimums can change the result.
Can volume convert exactly to tonnes?
No. Weight depends on material, moisture, and gradation. Use the supplier’s density for a reliable estimate.