How we worked it out
Updated as you change the numbers.
- Area = length × width = 20 ft × 4 ft = 80 sq ft.
- Volume = area × depth = 80 sq ft × 0.25 ft (3 in) = 20 cu ft.
- Cubic yards = 20 ÷ 27 = 0.741 yd³.
- 2 cu ft bags = 20 ÷ 2 = 10, rounded up to 10 bags.
Method and assumptions
Mulch is sold by volume. The calculator multiplies the area of the bed by the depth, then converts to cubic yards (27 cubic feet) and to bags. Bag counts are rounded up.
One cubic yard covers 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in and 81 sq ft at 4 in.
Tips
- Keep mulch a few inches away from tree trunks and plant stems; piling it against bark invites rot and pests.
- More than about 4 in can starve roots of air and keep the soil too wet.
- Bulk mulch is usually much cheaper per cubic yard than bags once you need more than 2 or 3 yards.
Questions
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How deep should mulch be?
University extension services generally recommend 2 to 4 in for wood mulch: enough to hold moisture and block weeds without smothering roots. Use the lower end for fine mulch and heavy soils.
Sources
- University of Minnesota Extension: Using mulches in home landscapes
- NIST Handbook 44, Appendix C: unit conversions
Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.