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Mulch Calculator
Mulch is where the bags-versus-bulk decision costs people real money: bags are easy and expensive, bulk is cheap and needs a driveway. Enter your beds and depth to get cubic yards, bag counts for the common sizes, and both totals side by side.
Your results
Shopping list — buy this much
The break-even is usually around 1 cubic yard: below it, bags win on total cost once delivery is counted; above it, bulk wins almost every time — if you have somewhere to dump it.
How it works
Cubic yards = cu ft ÷ 27 | Bags = cu ft ÷ bag size
The conversion everyone gets wrong once: one cubic yard is 13.5 bags of 2 cu ft (27 ÷ 2) — not "about ten." Underestimate the bag count by that margin and you're making a second trip with the car already smelling of cedar.
How deep should mulch be?
| Situation | Depth |
|---|---|
| Annual refresh over existing mulch | 1–2 in |
| Standard beds, shrubs and trees | 3 in |
| New beds, weed-prone areas | 4 in |
| Around tree trunks | 3 in, pulled back 3–6 in from the bark |
Deeper is not better: past 4 in, mulch can shed water instead of absorbing it and starve shallow roots of oxygen. And the volcano — mulch piled against a trunk — rots bark and invites pests; flat and pulled back is the whole technique.
Worked example
A 10×10 ft bed at 3 in deep: 100 × 0.25 = 25 cu ft = 0.93 cu yd. In 2 cu ft bags that's 12.5, so 13 bags — $52 at $4 each. In bulk, the same job rounds to 1 cu yd at $35 before delivery. Two beds this size and bulk is cheaper even after a $60 delivery fee; one bed and the bags win. That crossover, right around a yard, is the entire mulch-buying game.
Frequently asked questions
How many bags of mulch are in a cubic yard?
13.5 bags of the standard 2 cu ft size (27 cu ft ÷ 2). For 3 cu ft bags it's 9 bags per yard; for 1.5 cu ft bags, 18. If your bed math says 2 yards, you're looking at 27 bags — the moment bulk delivery usually becomes the sane option.
How much mulch do I need for 100 square feet?
At 3 inches deep: 25 cu ft, which is 0.93 cu yd or 13 bags of 2 cu ft. At 2 in it's 9 bags; at 4 in, 17 bags. Depth is the lever — one extra inch over a big bed is a third more material.
Is bagged or bulk mulch cheaper?
Bulk, per cubic yard, by a wide margin — often half the bag price or less. But bulk adds a $40–80 delivery fee (or a truck bed you have to clean) and you move it by wheelbarrow. Under roughly 1 cu yd total, bags usually win on true cost; over it, bulk almost always does.
How deep should mulch be in flower beds?
3 inches for most beds. 2 in is fine for a seasonal refresh over existing mulch; 4 in for new beds or heavy weed pressure. Keep it a few inches away from trunks and stems, and never pile it against house siding — it holds moisture where you least want it.
How often should mulch be replaced?
Top it up annually — mulch decomposes (that's partly the point: it's feeding the soil) and fades. Most beds need 1–2 in of fresh mulch each spring to hold the 3 in working depth, not a full replacement. If the bed has built up past 4 in of old mulch, rake some out rather than adding more.
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About the author
Harrison Alley is a web publisher and data enthusiast based in Dallas, Texas. He built Urbarama’s remodeling calculators and maintains them.
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