Planting
Garden Soil Calculator
For in-ground beds and borders. The settlement allowance covers screened soil consolidating once it is spread and watered.
Screened soil and compost lose 10-20% of their volume once spread and watered.
Cubic feet per bag. Retail soil and compost bags run 0.75 to 1.5 ft³.
Quantity estimate for planning and buying. Rates vary by variety, region and product — check the label on what you actually buy.
How many bags of soil are in a cubic yard?
A cubic yard takes 27 bags at 1 cubic foot, 36 bags at 0.75 cubic feet, or 18 bags at 1.5 cubic feet.
At $3-4 a bag that is $80-145 per cubic yard against $20-45 for the same soil delivered in bulk, so bulk wins from about half a cubic yard up.
Whichever you buy, allow 10-20% for settlement. Screened soil arrives fluffed up from handling and loses that much volume once it is spread, raked and watered in — order the finished depth you want and you will end up with a dip.
Settlement is not optional
Screened soil and compost arrive aerated from handling and screening, and lose 10-20% of their volume once spread, raked and watered in. Order the finished depth you want and you will be short, and the shortfall shows up as a dip exactly where you did not want one.
The default allowance here is 15%. For a bed you are levelling to match a path or a lawn edge, that is worth having.
Bulk or bags
A cubic yard is 27 cubic feet, so it takes 27 bags at 1 ft³ or 36 at 0.75 ft³. At $3-4 a bag that is $80-145 per cubic yard against $20-45 delivered in bulk.
Bulk wins on price from about half a cubic yard up. Bags win when you cannot take a delivery, when the beds are scattered, or when you want to work through it over several weekends — a yard of soil tipped on the drive is a commitment for the day.
One warning worth more than the arithmetic: cheap bulk "topsoil" varies enormously, and unscreened subsoil sold as topsoil is a common problem. Ask whether it is screened, ask what it is, and look at it before it is tipped. Good soil smells earthy and crumbles; bad soil is grey, sticky, and full of stones and roots.
| Depth | Covers | Yards per 100 ft² | Bags at 1 ft³ per 100 ft² |
|---|---|---|---|
| 0.25 in | 1,296 ft² | 0.08 | 3 |
| 0.5 in | 648 ft² | 0.15 | 5 |
| 1 in | 324 ft² | 0.31 | 9 |
| 2 in | 162 ft² | 0.62 | 17 |
| 3 in | 108 ft² | 0.93 | 25 |
| 4 in | 81 ft² | 1.23 | 34 |
| 6 in | 54 ft² | 1.85 | 50 |
| 12 in | 27 ft² | 3.70 | 100 |
How deep to spread
For a new bed over unimproved ground, 6-8 inches of good soil worked into the top of the native soil beats 12 inches sitting on top of it — a sharp boundary between two soil types stops roots crossing and stops water draining. Break the interface up with a fork.
For topping up an existing bed, 1-2 inches annually is plenty and can go straight on the surface. Worms and weather will incorporate it.
Common questions
How many bags of soil in a cubic yard?
27 bags at 1 cubic foot, 36 at 0.75 cubic feet, or 18 at 1.5 cubic feet.
How much soil do I need for a 10x20 ft bed?
At 6 inches deep, 100 cubic feet or 3.7 cubic yards. With a 15% settlement allowance, order about 4.3 cubic yards.
Does garden soil settle?
Yes, 10-20% after spreading and watering. Order for the settled depth you want, not the loose depth you spread.
Is bagged or bulk soil cheaper?
Bulk, by a wide margin — roughly $20-45 per cubic yard against $80-145 in bags. Bulk wins from about half a cubic yard up.