Mulch Calculator
Cover beds at the right depth, first time.
Mulch Calculator
Volume (cu yd) = Area × (Depth in / 12) / 27; Bags = ceil(Cubic feet / bag volume)
Calculated instantly
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What This Calculator Does
The Mulch Calculator estimates how much mulch a bed needs in cubic yards, cubic feet, and bags. It uses the standard 2–3 inch application depth that suppresses weeds and retains moisture without smothering roots.
How It Works
Area times depth in feet gives cubic feet. Dividing by 27 gives cubic yards for bulk delivery. Dividing cubic feet by bag volume gives the number of sealed bags, rounded up. Weight is approximate because mulch density depends on wood type and moisture.
Example
A 300 sq ft bed at 3 inches deep needs 75 cubic feet, or 2.78 cubic yards. That is 38 bags at 2 cubic feet each, and roughly 1.11 tons at 0.4 tons per cubic yard.
Formula
Cubic yards = Area × (Depth in / 12) / 27Bags = ceil(Cubic feet / bag volume)Tons = Cubic yards × bulk densityReading the Results
Volume
Loose mulch volume in cubic yards, the unit bulk suppliers use.
Bags needed
Sealed bags to buy, rounded up. A standard bag is 2 cubic feet in the US and 50 litres in metric markets.
Sources and References
USDA Natural Resources Conservation Service — mulching
Apply 2–3 inches around plants
NRCS extension guidance recommends a 2–3 inch layer and keeping mulch clear of stems.
University extension services — landscape mulch
Excess depth reduces oxygen to roots
Extension publications warn against mulch volcanoes and layers deeper than 3–4 inches.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
How deep should mulch be?
Two to three inches is standard for weed suppression and moisture retention. More than four inches can reduce oxygen at the roots and encourage rot around trunks.
How many bags of mulch are in a cubic yard?
At 2 cubic feet per bag, 13.5 bags make one cubic yard. Suppliers usually round to 13 or 14 bags for planning.
Should I remove old mulch first?
Not every year. Rake it to break the crust, then top up to the target depth. If the layer is already deeper than 4 inches, remove some before adding more.
Does mulch volume shrink?
Yes. Organic mulch decomposes and settles, typically losing 10–20% of its volume over a season. Order slightly extra if you want to maintain the full depth.