Bags needed
25
Mulch Calculator
How much mulch your beds need — in cubic yards and in bags, at the depth you choose.
Right across the bed, through the middle.
2 to 3 in is normal. Deeper is not better.
Same size each.
Printed on the bag. 2 cu ft is the common one.
1.85 cubic yards
Or 25 bags of 2 cubic feet.
Cubic feet
50.0
Cost in bags
—
Area covered
200 ft²
Check your bag size. Most bagged mulch in the US is 2 cubic feet,
but 1.5 and 3 cubic foot bags are both sold. The size is printed on the front. Pick
the right one above or the bag count will be wrong.
How this is worked out
Mulch is sold loose by the cubic yard or bagged by the cubic foot. Both come from the same volume.
Rectangle: length (ft) × width (ft) × depth (ft) = cubic feet
Circle: 3.14159 × radius (ft)² × depth (ft) = cubic feet
Then cubic feet ÷ 27 = cubic yards, and
cubic feet ÷ bag size = bags.
Worked example — a 20 ft × 10 ft bed, 3 in deep
- Depth in feet:
3 ÷ 12 = 0.25 ft - Volume:
20 × 10 × 0.25 = 50 cubic feet - In yards:
50 ÷ 27 = 1.85 cubic yards - In 2 cu ft bags:
50 ÷ 2 = 25 bags
Bags per cubic yard, and what a yard covers
| Bag size | Bags per cubic yard |
|---|---|
| 1.5 cubic feet | 18 |
| 2 cubic feet | 13.5 |
| 3 cubic feet | 9 |
| Depth | Area one cubic yard covers |
|---|---|
| 1 inch | 324 sq ft |
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |
Past about 10 or 12 bags it is usually cheaper to buy a yard loose and shovel it, if you have somewhere for the pile to go.
Questions people ask
How deep should mulch be?
2 to 3 inches for most beds. That is enough to hold moisture and keep weeds down. Deeper than 4 inches starts to work against you: water struggles to reach the roots and the mulch can go sour underneath.
Should mulch touch the trunk of a tree?
No. Keep it a few inches clear of trunks and stems. Piling mulch against bark holds moisture there and rots it. The "mulch volcano" you see around street trees is the wrong way to do it.
How often do I need to top it up?
Most beds need an inch or so a year as the old mulch breaks down. Measure what is there, work out the difference, and only order that. You rarely need to start again.
Bags or bulk?
Bags are easier to carry, store and spread a little at a time. Bulk is cheaper per yard and means no plastic, but you need somewhere to tip it and a free afternoon. The crossover is usually around 10 to 12 bags.
Is this the same for soil or compost?
The volume maths is identical — area times depth, divided by 27. Only the bag sizes change, and soil is much heavier than mulch, so check what your car or barrow can actually take.