Quick answer
Multiply length by width by depth in feet to get cubic feet, then divide by 27 for cubic yards. One cubic yard covers about 108 square feet at 3 inches deep and equals 13.5 bags of 2 cubic foot mulch.
How much mulch, soil, or gravel for common areas
Cubic yards by coverage area and depth, including an 8 percent buffer. The last column is the bag count at 3 inches deep.
| Area | 2 in deep | 3 in deep | 4 in deep | 2 cu ft bags (3 in) |
|---|---|---|---|---|
| 25 sq ft | 0.17 cu yd | 0.25 cu yd | 0.33 cu yd | 4 bags |
| 50 sq ft | 0.33 cu yd | 0.5 cu yd | 0.67 cu yd | 7 bags |
| 100 sq ft | 0.67 cu yd | 1 cu yd | 1.33 cu yd | 14 bags |
| 150 sq ft | 1 cu yd | 1.5 cu yd | 2 cu yd | 21 bags |
| 200 sq ft | 1.33 cu yd | 2 cu yd | 2.67 cu yd | 27 bags |
| 300 sq ft | 2 cu yd | 3 cu yd | 4 cu yd | 41 bags |
| 500 sq ft | 3.33 cu yd | 5 cu yd | 6.67 cu yd | 68 bags |
| 1,000 sq ft | 6.67 cu yd | 10 cu yd | 13.33 cu yd | 135 bags |
Find your area by multiplying length by width. For a circle, use 3.14 x radius x radius.
How do you calculate cubic yards of mulch, soil, or gravel?
Mulch, topsoil, compost, and gravel are all sold by volume, so one formula covers them. The calculator converts your depth from inches to feet, multiplies by the area, adds a small buffer for uneven ground, and reports the result both as cubic yards for bulk delivery and as a bag count.
It also prices both options side by side. Bags usually win for small beds you can load in one trip. Bulk usually wins once you need a cubic yard or more, as long as the delivery fee and drop location work for you.
The formula
- Cubic feet = length x width x (depth in inches / 12)
- Adjusted cubic feet = cubic feet x (1 + waste %)
- Cubic yards = adjusted cubic feet / 27
- Bags = adjusted cubic feet / bag size, rounded up
Worked example
With the starting values in the calculator (Length: 20 ft, Width: 6 ft, Depth: 3 in, Waste buffer: 8%, Bag size: 2 cu ft, Bag price: $4, Bulk price: $45/cu yd), the result is 1.2 cubic yards at an estimated $54 bulk or $68 bagged.
- Cubic feet = 20 x 6 x (3 / 12) = 30
- After waste = 30 x 1.08 = 32.4 cu ft
- Cubic yards = 32.4 / 27 = 1.2
What this calculator assumes
- The area is a rectangle. Split odd shapes into rectangles and add the results.
- An 8 percent buffer covers uneven ground and settling.
- Bag size defaults to 2 cubic feet, the most common mulch bag.
- Volume only. Gravel and soil are often sold by weight, so ask the supplier for tons per cubic yard.
Tips for a more accurate estimate
- Refreshing an old bed? Enter only the depth you are adding, not the total depth you want.
- Keep mulch 2 to 4 inches deep and pull it back from trunks and stems.
- Gravel is heavy. One cubic yard commonly weighs 2,400 to 2,900 pounds, so check your vehicle and trailer limits.
- Ask about delivery minimums before comparing bulk and bag prices.
Mulch, Soil, and Gravel Calculator FAQ
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic foot mulch, 18 bags of 1.5 cubic foot mulch, or 9 bags of 3 cubic foot mulch.
How much area does one cubic yard cover?
One cubic yard covers about 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches.
How much mulch do I need for 100 square feet?
At 3 inches deep, 100 square feet needs 25 cubic feet of mulch, which is 0.93 cubic yards or 13 bags of 2 cubic foot mulch. With a small buffer, plan on 1 cubic yard or 14 bags.
How deep should mulch be?
Two to three inches is common for fresh mulch. If an old layer remains, measure the actual depth you plan to add.
When is bulk cheaper than bags?
Bulk usually wins for larger jobs once delivery makes sense. Bags are easier for small beds and tight storage.
Can this calculate topsoil?
Yes. Use the same cubic yard math and adjust the bulk price to your local supplier quote.
Use this estimate as a planning starting point. Product coverage, waste, local prices, code rules, and site conditions can change the final amount.