How to calculate how much soil you need
Every soil job is a volume: the space you want to fill. Measure it in feet, multiply, and convert.
cubic feet = length (ft) × width (ft) × depth (in) ÷ 12 cubic yards = cubic feet ÷ 27
With the calculator’s default numbers, a 12 × 8 ft garden filled 6 inches deep:
- Area: 12 × 8 = 96 square feet
- Volume: 96 × (6 ÷ 12) = 48 cubic feet
- Cubic yards: 48 ÷ 27 = 1.78 cubic yards
- With 10% extra: 48 × 1.1 = 52.8 cubic feet = 1.96 cubic yards, or 53 one-cubic-foot bags
For a circle, use 3.14 × radius × radius for the area. An 8 ft round bed has a 4 ft radius, so the area is 3.14 × 16 = 50.3 square feet. At 6 inches deep that is 25.1 cubic feet, or 0.93 cubic yards.
For pots the calculator switches to inches, because that is how pots are measured, and it gives the answer in dry quarts and liters as well. The potting soil calculator has a full pot-size chart.
Pick the right soil for the job
The calculator’s material list sets the weight it uses for tons. It also helps to know which soil you are actually buying.
| Soil | Best for | Typical depth | Weight per cubic yard, about |
|---|---|---|---|
| Topsoil | Lawns, grading, the base of new beds | 4–6 in for lawns | 1 to 1.4 tons |
| Garden soil (topsoil + compost) | In-ground vegetable and flower beds | 6–8 in for new beds | 0.8 to 1.2 tons |
| Raised bed mix | Filling raised beds | the full bed depth | 0.7 to 1 ton |
| Compost | Amending and top-dressing beds | 1–3 in | 0.4 to 0.7 tons |
| Potting mix | Pots, planters, window boxes | fill to 1 in below the rim | 0.2 to 0.4 tons |
| Top-dressing mix | Thin layers on lawns, filling dips | ⅛–½ in | 1.1 to 1.4 tons |
Weights are ranges because soil holds water. A load after a week of rain can weigh far more than the same load in a dry spell. If you need tons, ask the supplier for their own figure.
Not sure what the difference is between the first two? See topsoil vs garden soil.
Cubic feet, cubic yards and liters
Bags are labelled in cubic feet or quarts, bulk soil is sold in cubic yards, and some products use liters. These conversions cover all of them:
| Cubic feet | Cubic yards | Liters | Bags of 1.5 cu ft |
|---|---|---|---|
| 1 | 0.04 | 28.3 | 1 |
| 5 | 0.19 | 142 | 4 |
| 10 | 0.37 | 283 | 7 |
| 13.5 | 0.5 | 382 | 9 |
| 27 | 1 | 765 | 18 |
| 54 | 2 | 1,529 | 36 |
| 81 | 3 | 2,294 | 54 |
Useful fixed numbers: 1 cubic yard = 27 cubic feet = 0.765 cubic meters. 1 cubic meter = 1.31 cubic yards = 35.3 cubic feet. 1 cubic foot = 25.7 US dry quarts.
Measuring tips that save a second delivery
- Measure the inside of beds. Boards take up space. A raised bed that is 4 × 8 ft on the outside, built from 1.5-inch-thick lumber, is about 3.75 × 7.75 ft inside, roughly 9% less soil.
- Average uneven depths. If the ground dips, measure the depth you need at four or five spots and use the average.
- Split odd shapes. Break an L-shape or a curved border into rectangles and circles, run each, and add them up. For a triangle, use half of base × height.
- Round up, not down. Bulk yards usually deliver in half or whole yards, and a second small delivery tends to cost more than a little extra soil.
For a step-by-step walk-through with five worked examples, read how much topsoil do I need.
All results are estimates. Settling, moisture and how firmly the soil is packed all change the real amount, so check quantities with your supplier before you order.
Questions gardeners ask
- How do you calculate cubic yards of soil?
- Multiply length × width × depth, all in feet, to get cubic feet, then divide by 27. Depth in inches becomes feet when you divide it by 12. A 12 × 8 ft bed filled 6 inches deep is 12 × 8 × 0.5 = 48 cubic feet, or 1.78 cubic yards.
- How many cubic feet are in a yard of soil?
- 27. A cubic yard is 3 ft × 3 ft × 3 ft. That is also 36 bags of 0.75 cubic feet or 27 bags of 1 cubic foot.
- How many liters is a cubic foot of soil?
- About 28.3 liters. A cubic yard is about 765 liters, or 0.765 cubic meters.
- Does the soil type change how much I need?
- Not the volume: a space of 48 cubic feet needs 48 cubic feet of any soil. The type changes the weight, the price and how much the soil settles, which is why the calculator lets you choose it.
- How much extra soil should I buy?
- Around 10 percent covers settling and uneven ground for most beds. Loose, fluffy mixes and compost settle more than screened topsoil, so add a little more for deep beds.