Mulch Calculator
Work out how many 2 cubic foot bags of mulch cover your beds at a 2-4 inch depth, plus total cost at your price per bag.
How this calculator works
Mulch is most commonly bought in bags at a garden center, so this calculator converts your bed’s volume directly into bag count using the standard 2 cubic foot bag size found on most mulch bags.
Formula: Cubic yards = (Length ft × Width ft × Depth ft) ÷ 27. Bags = (Cubic yards × 27) ÷ 2.
Worked example
A 10 ft × 10 ft bed at a 3-inch depth:
- Depth in feet: 3 ÷ 12 = 0.25 ft
- Cubic yards: (10 × 10 × 0.25) ÷ 27 ≈ 0.926 yd³
- Bags: (0.926 × 27) ÷ 2 ≈ 12.50 bags
- At $4/bag, that’s $50.00.
Coverage reference
| Bed size | Depth | Bags needed (2 cu ft) |
|---|---|---|
| 10 ft × 10 ft | 3 in | ~12.5 bags |
| 20 ft × 10 ft | 3 in | ~25.0 bags |
| 30 ft × 15 ft | 3 in | ~56.3 bags |
How to measure your beds
Measure each bed’s length and width along the ground, not around plant canopies, and use 3 inches as a reasonable middle-ground depth unless you have a specific reason to go shallower or deeper. For beds with a lot of existing mulch, measure the remaining depth and only calculate the top-up amount needed to reach your target depth.
Frequently asked questions
How many bags of mulch do I need per cubic yard?
About 13.5 bags, since a standard mulch bag holds 2 cubic feet and a cubic yard is 27 cubic feet (27 ÷ 2 = 13.5). This calculator applies that same 2 cubic foot bag size to your entered area and depth.
How deep should mulch be applied?
2 to 4 inches is the standard range for most garden beds. Less than 2 inches doesn't suppress weeds effectively, while more than 4 inches can hold excess moisture against roots and stems and may starve the soil of oxygen.
Why is waste not included on this calculator?
Mulch spreads and settles fairly predictably compared to compactable aggregates like gravel, and it's usually applied in a top-up layer rather than a precise structural fill, so most people just buy the calculated amount and adjust visually rather than budgeting a fixed waste percentage.
Should mulch touch the base of trees or shrubs?
No — keep mulch pulled back 2-3 inches from tree trunks and plant stems. Piling mulch directly against bark (sometimes called a 'mulch volcano') traps moisture against the trunk and can lead to rot and pest problems.
Does bagged or bulk mulch work out cheaper?
Bulk mulch delivered by the cubic yard is almost always cheaper per unit once you need more than roughly 3 cubic yards (about 40 bags), but bagged mulch is more convenient for small beds or when you don't have truck access to the delivery spot.
Estimates only. Verify quantities with your supplier before purchasing.