Mulch Calculator
Enter the length, width, and depth of your bed to find how many cubic yards and bags of mulch you need. Mulch is sold by the cubic yard and in 2 or 3 cubic foot bags, with 2–3 inches the usual depth.
How to calculate mulch
Multiply length × width × depth in feet to get cubic feet, then divide by 27 for cubic yards (how bulk mulch is sold). Bagged mulch usually comes in 2 cubic foot bags (hardwood and dyed) or 3 cubic foot bags (bark and nuggets), so divide the cubic feet by the bag size and round up. Depth is entered in inches here, so it is divided by 12 first. Use 2–3 inches over an existing bed and up to 4 inches for a fresh bed or weed suppression.
Cubic yards = (L ft × W ft × Depth ft) ÷ 27 · Bags = ft³ ÷ bag volume (2 or 3 ft³)
Worked example
A 20 ft × 10 ft garden bed mulched 3 inches deep.
- Depth = 3 in ÷ 12 = 0.25 ft
- Volume = 20 × 10 × 0.25 = 50 ft³
- Cubic yards = 50 ÷ 27 = 1.85 yd³
- Bags = 50 ÷ 2 = 25 (2 ft³ bags) or 50 ÷ 3 = 17 (3 ft³ bags)
Result: 1.85 cubic yards, which is 25 two-cubic-foot bags or 17 three-cubic-foot bags
Frequently asked questions
How much mulch do I need?
Multiply the bed's length × width × depth in feet to get cubic feet, then divide by 27 for cubic yards. A 20 × 10 ft bed at 3 inches deep needs about 1.85 cubic yards, which is 25 two-cubic-foot bags. Buying bulk by the yard is usually cheaper once you pass about half a yard (roughly 13 bags).
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals about 14 of the standard 2 cubic foot bags, or 9 of the larger 3 cubic foot bags. That is why bulk delivery beats bags once you need more than roughly a dozen.
How deep should mulch be?
Aim for 2–3 inches on an established bed and up to 3–4 inches on a new bed or where you want to suppress weeds. Deeper than 4 inches can starve roots of air and water, and keep mulch a couple of inches clear of tree trunks and plant stems.
How much area does a yard of mulch cover?
One cubic yard covers about 162 ft² at 2 inches deep, 108 ft² at 3 inches, or 81 ft² at 4 inches. The deeper the layer, the less ground a yard covers.
Should I order extra mulch?
Add about 5–10% for uneven ground and settling, and round up to the nearest half or full yard when ordering bulk. It is easier to spread a little extra than to place a second small order.