Mulch Coverage and Cost Calculator
Estimate mulch volume, bag quantities and the cost difference between bagged and bulk supply.
What this tool calculates
Area multiplied by depth gives cubic metres. The calculator adds your allowance, converts the result to litres, rounds bag quantities up and compares estimated bagged and bulk material costs.
How to use it
Measure each garden section separately and add the areas. Exclude paths, buildings and large rocks. Choose a depth appropriate to the mulch and plants, then enter local bag sizes and delivered bulk pricing.
Useful examples
- Ordering mulch for a revegetation or community planting day.
- Comparing trailer-load delivery with garden-centre bags.
- Budgeting weed suppression around trees and garden beds.
Important limits
Bulk sellers may round to half or whole cubic metres and charge delivery. Slopes, coarse pieces, settling and irregular bed edges change coverage. Keep mulch away from trunks and stems where required.
Measuring irregular beds
Break curved or irregular beds into smaller rectangles and triangles, calculate each area and add them. It is usually safer to order a little extra than to leave thin patches, but an excessive layer can hold too much moisture or interfere with airflow around some plants.
Worked example
Covering 50 square metres to 7.5 cm requires 3.75 cubic metres before allowance. Adding 10% gives 4.13 cubic metres or 4,125 litres. That equals 83 fifty-litre bags after rounding, allowing a direct price comparison with local bulk supply.
Mulch depth at a glance
Light top-up over an existing layer
Common starting estimate for established beds
Deeper coverage where plants and mulch type allow
These are planning examples, not universal horticultural rules. Confirm a suitable depth for the mulch material, soil, climate and plants, and keep material clear of trunks, crowns and building edges where required.
Frequently Asked Questions
Divide centimetres by 100. A 5 cm layer is 0.05 m, and a 7.5 cm layer is 0.075 m. The calculator performs this conversion before multiplying by the area.
Suppliers sell whole bags, so a result of 82.5 bags requires 83 bags. Bulk suppliers may instead round to their minimum order increment.
No. Enter the material price per cubic metre, then add delivery, trailer hire or minimum-order charges separately when comparing the final cost.
Ten percent is a practical starting allowance for settling, uneven ground and measurement error. Use a smaller or larger allowance when your measurements, site and mulch type justify it.