Mulch Calculator
Find how many cubic yards of mulch you need and how many bags to buy.
This calculator runs entirely in your browser. Nothing you enter is uploaded.
How to use this tool
Measure the area you want to cover. Enter the bed length and width in feet, then the depth you want in inches (most beds use 2 to 4 inches). Pick the bag size you plan to buy, then press Calculate mulch. The tool shows the square feet of coverage, the total volume in cubic feet and cubic yards, and how many bags you need. For an odd-shaped area, break it into rectangles, calculate each one, and add the results.
The formula for mulch in cubic yards
cubic feet = area x (depth in inches / 12)
cubic yards = cubic feet / 27
bags needed = round up( cubic feet / bag size )
Mulch and most landscaping material are sold by the cubic yard in bulk or by the bag at the store. Depth is the only measurement given in inches, so it is divided by 12 to convert it to feet before multiplying. One cubic yard equals 27 cubic feet, which is why the soil volume in cubic yards comes from dividing by 27. The same math works for topsoil, compost, gravel, and other landscaping material volume.
A real example
Say your flower bed is 20 feet long and 10 feet wide, and you want 3 inches of mulch. The area is 20 x 10 = 200 square feet of coverage. The depth in feet is 3 / 12 = 0.25 feet. Volume is 200 x 0.25 = 50 cubic feet, which is 50 / 27 = about 1.85 cubic yards. Using 2 cubic foot bags, you need 50 / 2 = 25 bags. If a bulk yard sells by the cubic yard, you would order 2 cubic yards to be safe.
Common questions
How deep should mulch be?
For most garden beds and around trees, 2 to 4 inches works well. Less than 2 inches lets weeds through, and more than 4 inches can hold too much moisture against roots. A 3 inch depth is a common middle ground.
How many bags of mulch are in a cubic yard?
It depends on the bag size. A cubic yard is 27 cubic feet, so it equals about 13.5 bags of 2 cubic feet, 18 bags of 1.5 cubic feet, or 9 bags of 3 cubic feet.
Can I use this for topsoil, compost, or gravel?
Yes. The volume math is the same for any landscaping material volume measured by length, width, and depth. Just enter your dimensions and read the cubic yards. Gravel and soil are heavier than mulch, so check weight limits if you are hauling it yourself.
Why convert to cubic yards?
Bulk suppliers price and deliver by the cubic yard because it is a larger, standard unit. Bagged mulch is sold in cubic feet at the store. This tool gives you both so you can compare buying in bulk versus by the bag.
Should I round bags up or down?
Always round up. You cannot buy a partial bag, and a little extra covers settling and uneven spots. This calculator rounds the bag count up to the next whole bag for you.
This is an estimate for planning and educational use. Actual coverage varies with mulch type, settling, and how evenly it is spread. Confirm amounts with your supplier before a large order.