Mulch Calculator
Find out how many cubic yards or bags of mulch you need.
A 2\u20133 inch layer is ideal for beds. Keep mulch a few inches away from trunks and stems.
Every spring, garden centers watch the same scene: someone eyeballs their flower beds, buys eight bags of mulch, and comes back twice more before the weekend is over. Our mulch calculator above ends that cycle — enter your bed dimensions and depth, and you’ll know your exact volume in cubic feet, cubic yards, and bags.
The Mulch Math
Volume (cu ft) = Length (ft) × Width (ft) × Depth (in) ÷ 12
Cubic yards = Volume ÷ 27
A 20 × 4 ft bed mulched 3 inches deep needs 20 cu ft — that’s 10 two-cubic-foot bags, 7 three-cubic-foot bags, or about 0.74 cubic yards in bulk.
For irregular beds, break the shape into rectangles and add them up, or measure the bed’s rough average length and width. For circular beds around trees, use radius × radius × 3.14 for the area in square feet.
How Deep Should Mulch Be?
Depth is where mulch either works or fails:
2–3 inches is the sweet spot for most beds. That’s enough to suppress weeds, hold soil moisture, and moderate soil temperature.
1 inch or less looks tidy for a month, then weeds push through. Fine mulches (like shredded leaves or grass clippings) can work at 2 inches; coarse mulches (bark nuggets) need 3–4.
More than 4 inches suffocates roots and keeps soil soggy — more is not better.
And the golden rule: keep mulch 2–3 inches away from trunks and stems. The “mulch volcano” piled against a tree trunk traps moisture against bark and invites rot and pests.
Bagged vs. Bulk: Which Is Cheaper?
The crossover point comes fast. Bagged mulch typically costs 2–3 times more per cubic yard than bulk delivery:
- Under ~1 cubic yard (13–14 bags): buy bags. Easier to transport, store, and spread in small spaces.
- 1–2 yards: it depends on delivery fees in your area — do the math both ways.
- Over 2 yards: bulk delivery almost always wins, even with the delivery charge.
One cubic yard equals 13.5 two-cubic-foot bags — a useful conversion when comparing prices. A standard pickup bed holds about 2 loose cubic yards of mulch.
Choosing a Mulch Type
Shredded hardwood — the all-purpose choice; knits together and stays put on slopes. Bark nuggets — long-lasting and decorative, but float away in heavy rain. Cedar — naturally insect-resistant and slow to decompose; costs more. Dyed mulches — hold color longest; buy from reputable suppliers to avoid dyed construction debris. Compost or leaf mold — feeds the soil best, but needs topping up yearly.
Organic mulches all decompose eventually — that’s a feature, not a flaw, since they enrich the soil. Expect to refresh a 3-inch layer with an inch or so annually.
Frequently Asked Questions
How many bags of mulch are in a cubic yard? 13.5 bags at 2 cu ft each, or 9 bags at 3 cu ft each.
How much does a cubic yard of mulch weigh? Dry hardwood mulch runs 400–800 lbs per yard; wet mulch can approach 1,000 lbs. Most sedans shouldn’t haul more than a few bags; a yard of mulch belongs in a truck or trailer.
Should I remove old mulch before adding new? Usually no. Rake and fluff the old layer, then top up to your target depth. Only strip old mulch if it’s matted, moldy, or already 4+ inches deep.
When is the best time to mulch? Mid-to-late spring, after the soil has warmed, and optionally again in late fall to insulate roots for winter.
Estimates are for planning purposes. Bag yields vary slightly by product and moisture content.