How to use the mulch and gravel calculator
- Choose the material: mulch, gravel, topsoil or sand.
- Add each area you want to cover as a rectangle, circle or triangle, with its dimensions in feet.
- Enter the depth in inches and keep or change the 10% waste allowance.
- Read cubic yards, bags, tons and the delivery note. Edit the weight, bag size or load size if you know better numbers, and add prices for a cost estimate.
Formula
Cubic feet = area in square feet x depth in inches / 12
Cubic yards = cubic feet / 27
With waste = cubic yards x (1 + waste percent)
Bags = cubic feet with waste / cubic feet per bag, rounded up
Tons = cubic yards with waste x tons per cubic yard
Depth is divided by 12 to turn inches into feet so that it matches the area in square feet. The tons per cubic yard figure is a typical approximation that you can override.
Worked example: a 20 ft by 10 ft flower bed, 3 inches of mulch
Area is 20 x 10 = 200 sq ft. Volume is 200 x (3 / 12) = 50 cubic feet, which is 50 / 27 = 1.852 cubic yards.
With a 10% waste allowance the volume is 55 cubic feet, or 2.037 cubic yards.
In 2 cubic foot bags that is 55 / 2 = 27.5, so 28 bags.
At the typical 0.3 tons per cubic yard for mulch the load weighs about 0.61 tons. Gravel at 1.4 tons per cubic yard would weigh about 2.85 tons for the same bed.
Choosing a depth
Depth matters more than most people expect, because the volume is proportional to it. Doubling the depth doubles the material. Many gardeners spread mulch a few inches deep, and gravel paths and driveways usually need more depth for the base than for a decorative top layer. Use the depth recommended for your product and site, and remember that a thick layer against a tree trunk or house siding can cause problems.
Yards, bags and tons
Bags are convenient for small beds, but they cost more per cubic foot than bulk. A cubic yard is 27 cubic feet, which is 13.5 two-cubic-foot bags. Past a few yards, bulk delivery is usually the better deal.
Weight matters when you are loading a trailer or paying by the ton. Mulch is light and varies a lot with moisture. Gravel and sand are heavy. The weights in this tool are typical approximations, so use your supplier figure when you have it.
Splitting irregular beds
Beds that curve are best split into a few rectangles, circles and triangles. A slightly generous estimate is fine because the waste allowance covers the difference. For help with the shapes, try the square footage calculator, and for a patio base see the paver calculator.
Assumptions and limits
- Tons per cubic yard are typical approximations (mulch 0.3, gravel 1.4, topsoil 1.1, sand 1.35). Moisture, type and particle size change the real number, and you can override it.
- The bag size (2 cubic feet) and the delivery load size (10 cubic yards) are labeled assumptions you can edit.
- Depth is uniform across every area. Mounded or sloped beds are not modeled.
- Compaction and settling are not calculated separately. Use the waste allowance if you expect material to compact.
- Cost uses only the prices you enter and leaves out delivery fees, tax and minimum orders.
Frequently asked questions
How many cubic feet are in a 2 cubic foot bag of mulch?
By definition a 2 cubic foot bag holds 2 cubic feet. You need 13.5 of them to make a cubic yard, because a cubic yard is 27 cubic feet. Check the bag because sizes differ.
How deep should mulch be?
Follow the guidance for your plants and local conditions. Many gardeners use a layer of a few inches, and this tool lets you enter any depth to see how the quantity changes.
Does one cubic yard of gravel weigh the same as mulch?
No. A cubic yard of gravel is several times heavier than a cubic yard of mulch. That is why the tool shows weight in tons, using a typical value for each material that you can replace.
Can I use this for a driveway base?
Yes, pick gravel, enter the driveway area and the base depth. Ask a local supplier which size of stone suits your use, and check any depth rules from the project plan or code.
What does the delivery note mean?
It shows what fraction of a single delivery load of the size you enter your order fills. Trucks carry different amounts, so ask your supplier before relying on it.