Mulch Calculator

Multiply the area you are covering, in square feet, by the depth in feet, then divide by 27 for cubic yards, or by 2 or 3 for the number of standard bags. For a rectangle that is length x width x (depth in inches / 12) / 27. Enter your numbers above and the calculator also gives the volume in cubic feet, two- and three-cubic-foot bag counts, and an approximate weight range.

A cubic yard is 27 cubic feet, so it holds 13.5 two-cubic-foot bags - round up to 14 - or exactly 9 three-cubic-foot bags. Bagged mulch usually costs more per cubic foot than bulk, so bags are most economical for beds under roughly a cubic yard.

One to three inches over a planting bed, and two to three inches around trees and shrubs, per University of Maryland Extension and Penn State Extension. Around a tree, keep the mulch an inch or two back from the trunk and off the root flare - a deep 'mulch volcano' piled against the bark traps moisture, invites rot and pests, and can starve the roots of oxygen.

Yes, as long as the combined depth stays in the recommended one-to-three-inch range. Rake and break up the old layer first if it has matted or crusted over, since a compacted layer sheds water instead of letting it through. If the existing mulch is already several inches deep, remove some before adding more.

Organic mulches - bark, wood, and pine - break down into the soil and usually need topping up every one to two years, or whenever the layer looks thin, faded, or compacted. Inorganic mulches such as rubber or stone last far longer but do not improve the soil as they age.

Spring, once the soil has warmed, is the most common time; a fall application also helps insulate roots over winter. Avoid mulching very early over cold, wet soil, which can keep the ground cool and slow plant growth.

Not the volume. Cubic yards, cubic feet, and bag counts depend only on the area and the depth. It does change the weight, because bark, shredded hardwood, pine, compost, and rubber mulch have very different bulk densities - which is why the calculator shows weight as a range and lets you narrow it by selecting a type.

Dry wood and bark mulch is roughly 400 to 800 pounds per cubic yard, and it gets heavier after rain. Shredded hardwood tends toward the top of that range; pine bark and pine straw are lighter. Compost and rubber mulch are considerably heavier. There is no single standard figure, so any weight shown here is an estimate for planning, not a precise value.