Mulch and Gravel Calculator
Short answer: Multiply length by width for square feet, multiply by depth in inches, and divide by 324 to get cubic yards. A 20 by 4 foot bed at 3 inches deep needs about 0.74 cubic yards, or 10 bags of 2 cubic feet.
How is this calculated?
One cubic yard is 27 cubic feet, and one inch is 1/12 of a foot, so square feet times inches divided by 324 gives cubic yards. Gravel weight varies by stone and moisture; the calculator uses common estimates of about 1.3 to 1.5 tons per cubic yard. Ask your supplier for their conversion before you order by the ton.
Frequently asked questions
How deep should mulch be?
Two to three inches is the common range for garden beds. Keep mulch a few inches away from tree trunks and house siding.
How many bags of mulch make a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet each. Round up to 14.
How much does a cubic yard of gravel weigh?
Roughly 1.3 to 1.5 tons depending on the stone size and how wet it is. Your supplier can give an exact figure for their material.