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Mulch Calculator
Most mulch mistakes come from depth, not area. Enter the bed and the material to get cubic yards, bag counts, and the depth university extension offices recommend.
- Cubic yards and bags
- Depth from extension guidance
- What a yard covers
Project measurements
What shape is the bed? Or enter the area if you know it
A straight bed along a wall or a fence line. Length times width.
Measurements Tape measure or decimals
What are you spreading? This sets the price and the weights
Bag size
Allowance For edges, settling, and spillage
How this number is built
Mulch math is simple. People go wrong on depth and on what a "yard" means.
A yard is 27 cubic feet, and 13.5 bags
A cubic yard is 3 × 3 × 3 ft, so 27 ft³, and since the standard bag is 2 cubic feet, a yard is 13.5 bags of it.
Two to three inches, and three is the maximum
University extension publications agree on 2–3 in of finished depth for a new bed: UF/IFAS, Maryland, Georgia, New Hampshire, Kentucky, and Vermont all land in the same range, and Maryland states plainly that 3 in is the maximum because roots need to breathe. Well-drained sites can carry a little more; clay soils want less. More is not better. Mulch deeper than 3 inches cuts off air to the roots.
Top up an inch a year, and do not just keep layering
Wood mulch breaks down over a season, so a bed wants about 1 inch a year to hold the 2–3 in layer. Layering fresh mulch on top of old year after year is specifically discouraged: it builds up a moisture-holding mat that roots cannot get through. Rake the old layer loose first, or take some out.
Keep mulch away from the trunk
Keep mulch clear of the trunk: at least 6 inches (Maryland, New Hampshire) and up to 12 (Florida), with the root flare left exposed. Piling it against the trunk (often called volcano mulching) suffocates roots, rots bark, makes habitat for rodents, and can make roots circle and strangle the tree years later. The same rule applies to shrubs.
Keep six inches off the house
Mulch piled against a foundation or siding is a termite-conducive condition in Mississippi State Extension's own words, and Kentucky's entomology department agrees. Leave at least a 6-inch mulch-free gap between the bed and the wall, and never let it touch wood siding or framing.
A wet yard of mulch is heavier than a half-ton pickup carries
Dry wood mulch runs about 600 lb a cubic yard, but the range is 400–800 dry and 800–1,000+ wet. And mulch is usually wet. A saturated yard of hardwood can be a thousand pounds, which is past the payload of a half-ton truck. Compost is heavier again at around 1,000 lb a yard. Have it delivered, or check what you are loading.
What a cubic yard covers
| Depth | 1 cu yd | 2 cu ft bag | 3 cu ft bag |
|---|---|---|---|
| 1 in | 324 sq ft | 24 sq ft | 36 sq ft |
| 2 in | 162 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 6 sq ft | 9 sq ft |
A cubic yard is 27 ft³ and covers 324 ÷ depth in inches square feet, so at the 3 inches mulch is supposed to be spread, one yard does 108 sq ft and one 2-cubic-foot bag does 8. Overbuying starts with planning on the 1-inch coverage figure and then spreading three inches. The table does not cover pine straw, which is sold in bales and covers 35–50 sq ft per bale at 3 in. No price on this page has a trade-association anchor behind it: mulch is a landscaping product, not a tracked commodity, so every figure is a retail listing and your supplier's price governs.
Measuring the bed first? The square footage calculator works out the area of any shape and carries it straight over here.
Where these numbers come from
- University extension consensus, six of them: UF/IFAS, University of Maryland (Trice, Dudley), UGA, UNH, University of Kentucky, and UVM all publish 2–3 inches for a new bed, with UMD stating 3 inches as the maximum. Guidance linked to the International Society of Arboriculture allows 2–4 inches on well-drained sites and about 2 on clay. Annual top-up of about an inch is the same consensus.
- MSU Extension 'Termite Conducive Conditions' and UK Extension ENTFACT 605 for the 6-inch foundation clearance. UMD and UNH for the 6-inch trunk clearance, UF/IFAS for 12 inches, and the volcano-mulching harms are documented across the same extension set.
- LSU AgCenter for the 3-inch initial layer, about ½ lb per square foot, reapplying to 1 inch, and the 25 to 30% settling. University of Missouri Extension (via AgEBB) gives 70 to 100 sq ft per bale and LSU about 50; supplier planning figures give 35 to 50.
- Municipal and state figures: City of St. Petersburg data via the Florida DEP yard-trash manual (mulch 550–650 lb/yd³, screened compost 800–1,000), a municipal wood-chip figure of about 600, and MRWMD's landscaping price sheet (about 400 for woodchips, 1,400 for compost). Moisture accounts for most of the difference.
- 2026 cost guides and retail listings only. Mulch has no USGS-style primary price anchor, because it is a landscaping product rather than a tracked mineral commodity, so unlike concrete and gravel these prices carry no trade or government source at all and must be read as retail listings. The bagged-versus-bulk split (bagged about 40 to 60% more per yard, bulk is cheaper past about 2 to 3 cubic yards, once delivery minimums no longer outweigh the savings) is from the same guides.
The other nine calculators
Every material, same layout, its own crew.
