Calculate soil from the area you want to fill and the depth you want to reach, or work backward from a volume you already have.
Soil Formula
When you know the area and the depth, the soil volume is the area multiplied by the depth, then increased by a small percentage for settling and waste.
Volume = Area * Depth * (1 + Waste)
When you already have a volume and want to know how many bags to buy, divide the volume by the size of one bag and round up.
Bags = Volume / BagSize
When you have a fixed volume of soil and want to know how deep it will go over an area, divide the volume by the area.
Depth = Volume / Area
To estimate weight, convert the volume to cubic yards and multiply by the soil density.
Weight = CubicYards * Density
- Volume is the amount of soil, usually in cubic feet or cubic yards.
- Area is the surface you are filling, in square feet.
- Depth is how deep the soil will sit, converted to feet so it matches the area.
- Waste is the extra fraction added for settling, compaction, and spillage, often 10 percent.
- BagSize is the volume of one bag, commonly 0.75, 1, 1.5, or 2 cubic feet.
- CubicYards is the volume divided by 27, since 27 cubic feet make one cubic yard.
- Density is the weight of one cubic yard, in tons.
The soil needed mode multiplies area by depth and adds waste, then reports cubic feet, cubic yards, bags, weight, and cost. The bags and cost mode starts from a volume you enter and converts it the same way. The depth mode divides a known volume by the area to show how thick the layer will be. The mix split mode takes a total volume and divides it into topsoil, compost, and other amendment shares based on the percentages you set.
Soil Coverage and Weight Reference
One cubic yard of topsoil covers different areas depending on how deep you spread it. Use this to sanity check the volume the calculator returns.
| Depth | Area covered by 1 cubic yard |
|---|---|
| 1 inch | 324 sq ft |
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 6 inches | 54 sq ft |
| 12 inches | 27 sq ft |
Weight depends on how dry or compacted the soil is. These are the density values the calculator uses for the tons estimate.
| Soil condition | Approximate weight per cubic yard |
|---|---|
| Dry or loose | 1.15 tons (about 2,300 lb) |
| Compacted | 1.50 tons (about 3,000 lb) |
| Wet | 1.70 tons (about 3,400 lb) |
Examples
Example 1. You have a raised bed that is 8 feet long and 4 feet wide, and you want 12 inches of soil. The area is 8 times 4, which is 32 square feet. The depth of 12 inches is 1 foot. The base volume is 32 times 1, which is 32 cubic feet. With 10 percent added for settling, that is 35.2 cubic feet, or about 1.3 cubic yards. Using 2 cubic foot bags, you would need 35.2 divided by 2, which is 17.6, so you buy 18 bags.
Example 2. You bought 1 cubic yard of soil and want to spread it over a 150 square foot bed. One cubic yard is 27 cubic feet. The depth is 27 divided by 150, which is 0.18 feet, or about 2.16 inches.
FAQ
How many bags of soil are in a cubic yard? One cubic yard is 27 cubic feet. Divide 27 by the bag size to get the count. That is 36 bags at 0.75 cubic feet, 27 bags at 1 cubic foot, 18 bags at 1.5 cubic feet, or about 14 bags at 2 cubic feet.
Why does the calculator add a waste percentage? Soil settles and compacts after it is placed, and some is always lost to spillage and uneven ground. Adding about 10 percent means you are less likely to run short and have to make a second trip.
Should I order bags or bulk soil? Bags are easier to handle for small beds and let you buy an exact count. Bulk soil by the cubic yard is usually cheaper per unit for larger projects, which is why the calculator also rounds the bulk order to the nearest quarter yard so you can compare both options.
