Mulch Calculator

Most garden beds use a 3 inch layer of mulch. Bags are 2 cubic feet, cubic yards are 27 cubic feet. Cost estimate assumes $4 per bag or $35 per yard for hardwood mulch.

Switch to bulk delivery once you pass roughly 1.5 cubic yards (40-50 bags) - bagged mulch costs twice as much per cubic foot at that scale.

Mulch is sold by volume: cubic yards (loose, in truck loads) or cubic feet (in bags, usually 2 cu ft). To know how much to buy, multiply your bed's area by the mulch depth you want, then convert to whichever unit your supplier uses. A 3 inch deep layer is the standard recommendation for most garden beds - deep enough to suppress weeds and retain moisture, shallow enough not to smother plants.

Our mulch calculator handles rectangular and circular beds, switches between imperial and metric, and shows you cubic yards, cubic feet, standard 2 cubic foot bag count, and a cost estimate. Use the numbers at the garden center or call your local landscape supply.

Step 1: Calculate area

Rectangle: length × width. Circle: π × radius². For an L-shaped bed, split it into two rectangles, calculate each, and add them together.

Step 2: Convert depth to feet

Mulch depth is usually given in inches but the area is in square feet. Divide depth by 12. So 3 inches becomes 3 / 12 = 0.25 ft.

Step 3: Multiply for cubic feet

volume = area × depth. A 10 ft × 4 ft bed at 3 in deep is 10 × 4 × 0.25 = 10 cu ft. That is 5 bags of 2 cu ft mulch.

Step 4: Convert to cubic yards (if buying loose)

Divide cubic feet by 27. The same 10 cu ft is 10 / 27 = 0.37 cu yd. Most suppliers will not deliver less than a full cubic yard, so order 1 cubic yard if buying in bulk.

Math: 1 cu yd = 13.5 bags of 2 cu ft each. At Home Depot, that is about $70-80 in bags vs $40-60 from a bulk supplier. The break-even including delivery fees is typically 3 cubic yards.

• 2 inches - minimum for established beds with no weed pressure
• 3 inches - standard recommendation for most garden beds and trees
• 4 inches - new beds, weed-prone areas, or for moisture retention in dry climates
• 6 inches or more - avoid; can suffocate roots and create a 'mulch volcano' that rots tree bark

How many bags of mulch in a cubic yard?

13.5 bags of 2 cubic foot mulch make one cubic yard. Some bags are 3 cubic feet - those are 9 per yard.

When should I apply mulch?

Late spring after the soil has warmed (mulching while soil is still cold keeps it cold longer). Refresh in early fall to insulate roots over winter.

Do I need to remove old mulch before adding new?

No, just rake the old mulch to break up any matted top layer and add 1-2 inches of new on top to refresh the color. Strip and replace entirely only every 3-4 years.

Will mulch hurt my plants?

Mulch helps almost every plant in a garden bed. Two situations where it can hurt: piled directly against stems or trunks (causes rot), or applied too thick (suffocates roots). Keep it under 4 inches and away from stems.

Is dyed mulch safe?

Most modern mulch dyes are iron oxide or carbon-based and considered safe. Older mulch (pre-2010 or no-name brands) sometimes used chromated copper arsenate-treated wood - avoid for vegetable gardens and play areas.

A cubic yard is 27 cubic feet. Divide by the bag size to get the bag count: a 2 cubic foot bag gives 13.5 bags per cubic yard, a 3 cubic foot bag gives 9. Coverage below is how much ground one cubic yard blankets at each spread depth.

Round bag counts up when you buy: you cannot buy half a bag, so 13.5 bags per yard means 14 bags in practice.

A yard of mulch means a cubic yard, which is 27 cubic feet. Divide that by the size of your bag to get the count. The most common bag size is 2 cubic feet, so a yard is 27 / 2 = 13.5 bags. If your store sells 3 cubic foot bags, a yard is 27 / 3 = 9 bags. Since you cannot buy a half bag, plan on 14 of the 2 cubic foot bags to match one cubic yard of loose mulch.

Going the other way is just as easy. Multiply your bag count by the bag size, then divide by 27 to get cubic yards. Twenty 2 cubic foot bags is 20 × 2 / 27 = 1.5 cu yd. Our mulch bag calculator does this conversion for you in both directions.

Mulch is measured by volume, so how much you need depends on both the area of your beds and how deep you spread it. Aim for 2 to 3 inches on established beds and refresh that top layer once a year as it breaks down and fades. Going deeper than 4 inches starts to smother roots.

Worked example: a bed that is 12 ft × 10 ft is 120 square feet. At 3 inches deep that is 120 × (3 / 12) = 30 cubic feet. Divide by 27 to get 30 / 27 = 1.1 cubic yards, or divide by 2 to get 30 / 2 = 15 bags of 2 cubic foot mulch. Feed your own bed size and depth into the mulch calculator above to get the cubic yards and bag count instantly.

How many bags is a yard of mulch?

It is 13.5 of the standard 2 cubic foot bags, or 9 of the larger 3 cubic foot bags, because one cubic yard equals 27 cubic feet. Buy 14 of the 2 cubic foot bags to cover a full yard with a little to spare.

How much mulch do I need?

Multiply your bed area in square feet by the depth in feet (inches divided by 12) to get cubic feet. Divide by 27 for cubic yards or by 2 for the number of 2 cubic foot bags. As a quick guide, one cubic yard covers about 108 square feet at a 3 inch depth.

How deep should mulch be?

2 to 3 inches is the sweet spot for most garden beds: enough to block weeds and hold moisture without suffocating roots. Use 2 inches on established beds and up to 4 inches on new or weed-prone areas. Keep mulch pulled back from stems and trunks.

How do I convert cubic yards to bags?

Multiply the cubic yards by 13.5 for 2 cubic foot bags, or by 9 for 3 cubic foot bags. For example, 2 cubic yards is 2 × 13.5 = 27 bags of the 2 cubic foot size.