Mulch calculator
Add up your bed areas, pick a depth, and see whether bags or a bulk delivery is the better buy. The calculator handles rectangular and round beds and totals them.
How the mulch calculator works
Mulch is sold by volume, in bags of 1.5, 2, or 3 cubic feet or in bulk by the cubic yard. The calculator takes your bed area in square feet, multiplies by the depth in feet, and converts the resulting cubic feet to bags and yards. Round beds use the circle formula, π × radius², so a 6 foot tree ring is about 28 square feet.
One cubic yard is 27 cubic feet, which is 13.5 two-cubic-foot bags or 9 three-cubic-foot bags. That ratio is the fastest way to compare a bag price against a bulk price.
Formula
cubic feet = area sq ft × depth in ÷ 12
bags = cubic feet ÷ bag size, rounded up. cubic yards = cubic feet ÷ 27.
Example: three beds totaling 300 square feet at 3 inches deep need 300 × 0.25 = 75 cubic feet. That is 38 two-cubic-foot bags or 2.8 cubic yards, so order 3 yards.
How deep should mulch be?
- 2 inches for topping up beds that already have mulch, and for fine shredded mulch that packs down.
- 3 inches for new beds. This is enough to suppress most weeds and hold moisture without smothering roots.
- 4 inches for coarse bark nuggets, which leave more air gaps.
- Keep mulch 2 to 3 inches away from tree trunks and plant stems. Piled "volcano" mulch traps moisture against bark and invites rot.
Need the bed itself built up first? The topsoil calculator uses the same math for soil and compost.
Common questions
How many bags of mulch are in a cubic yard?
13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet, or 18 bags of 1.5 cubic feet. If bulk mulch costs $35 a yard and 2 cubic foot bags cost $4, the bags work out to $54 a yard.
How much does a 2 cubic foot bag of mulch cover?
About 12 square feet at 2 inches deep, 8 square feet at 3 inches, or 6 square feet at 4 inches.
How much does a cubic yard of mulch weigh?
Dry shredded hardwood weighs 400 to 800 pounds per cubic yard; wet mulch can approach 1,000 pounds. A pickup bed holds 2 to 3 yards by volume, which is within the payload of most full-size trucks when the mulch is dry.
When is the best time to mulch?
Mid to late spring after the soil has warmed, and again in late fall to insulate roots. Mulching too early in spring keeps the ground cold and slows plant growth.