2-3 inches of mulch depth is standard for most garden beds — more than 4 inches can smother roots and encourage rot against stems.
Bulk (by the cubic yard) is cheaper than bagged material once you need more than about 2-3 cubic yards.
A standard bag of mulch or soil is commonly 2 cubic feet; gravel bags are often smaller — check the bag before buying.
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How deep should mulch be?
2-3 inches for most garden beds is standard. Go no deeper than 4 inches, and keep mulch a few inches back from plant stems and tree trunks to avoid trapping moisture against them.
Should I buy bagged or bulk material?
Bulk (delivered by the cubic yard) is usually cheaper past roughly 2-3 cubic yards. For smaller areas, bagged material avoids having a large pile delivered and is easier to store the rest of.
Does this work for gravel and topsoil too, not just mulch?
Yes — the volume formula is the same for any bulk material; only the bag size and price per cubic yard change, both of which you can adjust above.
How many 2-cubic-foot bags make a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags at 2 cubic feet each — round up to 14 bags in practice. Enter your own bag size above if it differs.