Bulk materials
Mulch Calculator
Enter your bed dimensions and how deep you want the mulch. You'll get cubic yards, the number of 2 cu ft bags, delivered weight, and whether bags or bulk works out cheaper at that volume.
Updated
Area to cover
Add a section for each part of the space. Odd shapes are easiest as two or three simple ones.
Area = length × width
Material and depth
Knits together on slopes better than chunky bark. The default choice for most beds.
2–3 in suits most beds. Past 4 in you start causing problems rather than solving them.
5% covers settling and uneven ground. Use 10% on rough or sloped sites.
The standard retail size.
Only affects the weight figures, never the volume. Typical range 400–900 lb/cu yd, wet material sits at the top.
Enter your measurements to see results.
Get mulch recommendations
Describe your beds and climate and the assistant will suggest a mulch type, depth, and refresh schedule, the numbers above stay exactly as calculated.
Written by AI from the figures above. The quantities themselves are calculated deterministically and are never generated by AI. Check anything consequential, permits, utility locates, and chemical labels especially, before acting on it.
How this is calculated
The calculation
Mulch is sold by volume, so the whole job is area times depth. The only trap is unit mixing, beds get measured in feet, depth gets chosen in inches, and mulch gets sold in cubic yards.
Convert the depth to feet first (divide inches by 12), multiply by the bed area in square feet to get cubic feet, then divide by 27 to reach cubic yards.
cubic yards = (area in sq ft × depth in inches ÷ 12) ÷ 27
Bag and coverage math
The standard retail bag holds 2 cubic feet. Since a cubic yard is 27 cubic feet, one cubic yard equals 13.5 bags, which is why bulk delivery starts beating bags somewhere around two yards for most people, once you account for the trips.
Coverage per bag falls as depth rises, and it falls fast. One 2 cu ft bag covers 12 sq ft at 2 inches deep, but only 6 sq ft at 4 inches.
| Depth | Coverage per bag | Bags per 100 sq ft |
|---|---|---|
| 1 in | 24 sq ft | 4.2 |
| 2 in | 12 sq ft | 8.3 |
| 3 in | 8 sq ft | 12.5 |
| 4 in | 6 sq ft | 16.7 |
How deep should mulch go?
Two to three inches is right for most beds. That is deep enough to block light from weed seeds and slow evaporation, and shallow enough that water and air still reach the roots.
Going past four inches starts causing problems rather than solving them: it can keep the soil surface waterlogged, and piling mulch against trunks and stems invites rot and rodent damage. Keep mulch a couple of inches clear of any woody stem.
If you are topping up an existing bed rather than starting fresh, measure what is already there and only add the difference. Beds that get a full three inches added every spring end up smothered.
Worked example
A typical front foundation bed
A bed running 30 ft along the house and 6 ft deep, mulched 3 inches deep with shredded hardwood.
- Area
- 30 ft × 6 ft = 180 sq ft
- Depth in feet
- 3 in ÷ 12 = 0.25 ft
- Volume
- 180 × 0.25 = 45 cu ft
- Cubic yards
- 45 ÷ 27 = 1.67 cu yd
- Bags
- 45 ÷ 2 = 23 bags
About 1.7 cubic yards, or 23 bags. At roughly $4.50 a bag that is $104 in bags against $50–90 for two yards delivered, close enough that the delivery fee decides it.
Frequently asked questions
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