This mulch calculator, which also handles topsoil, gravel and sand, tells you how many cubic yards, cubic feet and bags you need to cover a bed or path at a chosen depth. It also gives an approximate weight so you know whether a bulk delivery or a few trips with the car makes more sense.
How to Use the Mulch Calculator
- Choose the material: mulch, topsoil, gravel or sand.
- Pick the shape of the area. Use rectangle for beds and paths, and circle for round beds or rings around trees.
- Enter the length and width in feet, or the diameter for a circle.
- Enter the depth you want in inches. See the depth table below if you are unsure.
- Choose the bag size you plan to buy. Bagged mulch is most often 2 cubic feet.
How the Calculation Works
First the calculator finds the area in square feet. For a rectangle it multiplies length by width. For a circle it uses pi times the radius squared, where the radius is half the diameter.
Next it converts depth from inches to feet by dividing by 12, then multiplies area by depth to get cubic feet. Dividing cubic feet by 27 gives cubic yards, since one cubic yard is 3 x 3 x 3 feet. Bulk landscape suppliers sell by the cubic yard.
Bags are calculated by dividing cubic feet by the bag size and rounding up to a whole bag. The approximate weight uses a typical figure per cubic yard for each material: 0.4 tons for mulch, 1.1 tons for topsoil, 1.4 tons for gravel and 1.35 tons for sand. Actual weight varies with moisture and product, so treat it as a rough guide.
Worked example with the default values: a mulch bed 20 feet long and 4 feet wide, 3 inches deep, using 2 cubic foot bags.
- Area: 20 x 4 = 80 square feet
- Volume: 80 x 3 / 12 = 20 cubic feet
- Cubic yards: 20 / 27 = 0.74 cubic yards
- Bags: 20 / 2 = 10 bags
- Weight: 0.74 x 0.4 = about 0.3 tons of mulch
The same 80 square feet at 3 inches would weigh about 0.81 tons as topsoil or about 1.04 tons as gravel. For a round bed, the default 8 foot diameter covers about 50 square feet, which at 3 inches is 12.6 cubic feet, or 7 bags of 2 cubic feet.
Recommended Depth by Use
These are common rule of thumb depths. Local conditions, the product and your supplier’s advice may shift them a little.
| Use | Material | Typical depth |
|---|---|---|
| Refreshing existing mulch beds | Mulch | 1 to 2 in |
| New flower and shrub beds | Mulch | 2 to 4 in |
| Ring around trees (kept away from the trunk) | Mulch | 2 to 4 in |
| Weed suppression on bare areas | Mulch | 3 to 4 in |
| Top dressing an existing lawn | Topsoil or compost blend | 0.25 to 0.5 in |
| Preparing ground for a new lawn | Topsoil | 4 to 6 in |
| Filling raised garden beds | Topsoil or garden soil blend | Bed height, often 8 to 12 in |
| Garden paths and walkways | Gravel | 2 to 4 in |
| Decorative stone in beds | Gravel or river rock | 2 to 3 in |
| Base under pavers | Gravel base | 4 to 6 in for walkways and patios |
| Bedding layer under pavers | Sand | About 1 in |
Tips and Common Mistakes
- More mulch is not better. Piling mulch much deeper than 4 inches can keep soil too wet and limit air to roots. Keep mulch pulled back a few inches from tree trunks and plant stems.
- Measure irregular beds in pieces. Break curved or odd shaped beds into rough rectangles and circles, run each one, and add the results.
- Compare bags and bulk. A cubic yard holds 27 cubic feet, which is 13 to 14 bags of 2 cubic feet. For larger areas, bulk delivery is often cheaper per yard, even with a delivery fee.
- Allow for settling. Fresh topsoil and mulch settle after rain and watering. Many people order about 10 percent extra for soil fills.
- Check your vehicle’s limit. A cubic yard of gravel or soil can weigh more than a ton. That is often beyond what a small pickup bed or trailer should carry in one load.
Frequently Asked Questions
How much area does a cubic yard of mulch cover?
One cubic yard covers about 108 square feet at 3 inches deep, about 162 square feet at 2 inches, and about 81 square feet at 4 inches.
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet. In practice, that means 14 bags.
How deep should mulch be?
Two to four inches is the usual recommendation for beds. Use the lower end for fine mulch and refreshing old beds, and the higher end for coarse mulch or areas where you want stronger weed control.
Can I use this calculator for gravel and sand?
Yes. Choose gravel or sand from the material list. The volume math is the same for every material; only the approximate weight changes.