Garden beds
Mulch Calculator
Convert bed area and finished depth into cubic volume and complete bags, with enough allowance to account for settling.
Preparing calculator...
How to calculate it
- Measure the bed at its longest and widest points.
- Choose the finished mulch depth.
- Enter the volume printed on one bag.
Formula and assumptions
What the calculator is doing
Loose volume = length × width × finished depth × (1 + waste %); bags = ceil(loose volume ÷ volume per bag).
- Depth is converted from inches to feet or centimetres to metres.
- Imperial bulk volume is displayed in cubic yards while common bag volume remains cubic feet.
- The allowance can cover curved edges and settling, but it should not compensate for an incorrect bed depth.
Before checkout
Buying checklist
- Measure only the beds receiving material.
- Check existing depth before choosing the added depth.
- Read bag volume rather than bag weight.
- Keep mulch clear of trunks, stems, vents, siding, and drainage paths.
Avoid these errors
Common mistakes
Adding the target depth to an existing layer
Measure what is already present; a refresh often needs less material than a new bed.
Using bag weight as bag volume
Moisture and material type change weight, while the project is determined by volume.
Piling mulch against plants or buildings
The quantity may be correct while the placement still creates moisture and pest problems.
Frequently asked questions
How deep should mulch be?+
A refreshed bed often needs about 2 inches; a new bed may use 3 inches. Excess depth can retain too much moisture around plants.
How do I measure an irregular bed?+
Split it into rectangles, calculate each section, and add the results. A modest waste allowance covers curved edges.