The only formula that belongs on a mulch bag
Cubic feet = square feet × depth in inches ÷ 12. Cubic yards = cubic feet ÷ 27. Bags = cubic feet ÷ the cubic feet printed on the bag, then round up. There is no density in that chain. Mulch weight swings with water, and stores sell the volume.
A 2 cubic foot bag is 2/12 = 1/6 of a foot deep if you spread it over 12 square feet. That is the 2 inch coverage Scotts’ retailers print. At 3 inches the same bag covers 8 square feet. A 3 cubic foot bag covers half again as much: 18 square feet at 2 inches, 12 at 3. One yard is 13.5 of the small bags, which means 14 on the receipt, or 9 of the large ones exactly.
Worked bed: 20 by 5 feet, 3 inches
100 square feet × 3/12 = 25 cubic feet, or 0.93 cubic yards. Split into 2 cubic foot bags that is 12.5, so you buy 13 bags. Split into 3 cubic foot bags it is 8.33, so you buy 9 bags. The half bag is why the sheet shows the raw number beside the one you can carry. Buying 12 bags of the 2 cubic foot size leaves you a cubic foot short, which is a bare strip along a 5-foot edge.
The depth box opens at 3 inches because that is the layer Scotts describes for weed suppression on Nature Scapes, not because every mulch wants to be that thick. Pine straw and a top-up on last year’s bed are thinner jobs. Change the inches; don’t add a fake fluff factor on top.
Mistakes
- Dividing by 3 while holding 2 cubic foot bags. You will be short by a third.
- Typing 3 in the depth box when you meant 3 feet. That is a trench, not a bed.
- Trusting a calculator that opens at 1 inch or 6 inches while the paragraph next to it says something else. The number in the box is the order.
- Treating “compressed” marketing as a second yield. If the bag states cubic feet, use that number. If it only says the bale expands, it does not belong in this count until you know the expanded volume.
- Ordering a full yard for a bed that is 0.93 yards and then having nowhere to put the extra. Sometimes the extra is what you want. The sheet lets you see it before the truck is booked.
FAQ
How many 2 cubic foot bags are in a yard?
13.5. A cubic yard is 27 cubic feet, and 27 ÷ 2 = 13.5, so you buy 14 bags if you need a full yard and nothing less. Three cubic foot bags go exactly: 27 ÷ 3 = 9.
How much does one bag cover?
Coverage is the bag’s cubic feet divided by the depth in feet. A 2 cubic foot bag at 2 inches covers 12 square feet, which is what Scotts Nature Scapes lists. At 3 inches that same bag covers 8 square feet. A 3 cubic foot bag covers 18 square feet at 2 inches and 12 at 3 inches. The depth does the work, not the brand name.
Why does the depth start at 3 inches?
Scotts tells Nature Scapes buyers that a 3 inch layer blocks weeds by keeping light off the soil. It is a product instruction for that mulch, not a law for pine straw. Change the depth if you are only refreshing a bed that already has mulch.
Should I add extra for fluff?
Not unless the bag tells you the cubic feet are compressed and will grow. This sheet divides by the cubic feet printed on the bag. Scotts’ 2 cubic foot bag and its 12 square feet at 2 inches are the same arithmetic, so the label volume is the one to use.
Sources
- Scotts Nature Scapes Color Enhanced Mulch, 2 cu. ft. — The product is sold as a 2 cubic foot bag. Scotts says a three-inch layer blocks weeds.
- Scotts Nature Scapes coverage, retailer listing — Lists dry volume 2 cubic feet and 12 square feet of coverage at a 2 inch depth, which matches 2 ÷ (2/12).
- Jemasco hardwood mulch, 3 cubic foot bag — A real bag labeled 3 cubic feet. Coverage at 1 inch is 36 square feet, again the geometry: 3 × 12.
- The Calculator Site, mulch bag arithmetic — A cubic yard is 9 bags of 3 cubic feet. Used here only as a check on 27 ÷ 3, not as a yield.