The short answer
cubic yards of dirt = length (ft) × width (ft) × depth (ft) ÷ 27
Depth is usually measured in inches, so divide inches by 12 first: 3 in = 0.25 ft, 4 in = 0.33 ft, 6 in = 0.5 ft, 12 in = 1 ft. Then add an allowance: about 10% for dirt that will only be raked, 15–20% for dirt that will be tamped or settled. The dirt calculator does the arithmetic and also gives tons and truck loads.
Step by step
- Decide the finished height. Stake a string line or lay a straight board where the top of the dirt should be.
- Measure length and width in feet. Round to the nearest half foot.
- Measure the depth from the string down to the ground at several spots and average them.
- Multiply length × width × depth in feet to get cubic feet.
- Divide by 27 for cubic yards.
- Add your allowance and round up to what the supplier sells, usually whole or half yards.
How many cubic feet in a yard of dirt?
A yard of dirt, soil or sand always means a cubic yard: 3 ft × 3 ft × 3 ft = 27 cubic feet. That never changes with the material. What changes is the weight: a cubic yard of dry dirt is about 1 ton, and a yard of wet clay can be 1.4 tons or more.
| Cubic yards | Cubic feet |
|---|---|
| 0.5 | 13.5 |
| 1 | 27 |
| 2 | 54 |
| 3 | 81 |
| 5 | 135 |
| 10 | 270 |
Worked examples
Topping up a garden border, 30 × 3 ft, 3 in deep. 30 × 3 = 90 sq ft. 90 × 0.25 = 22.5 cu ft. 22.5 ÷ 27 = 0.83 yd³. Add 10% = 0.92 yd³, so order 1 yard, or about 25 one-cubic-foot bags (0.92 × 27 = 24.75 cu ft).
Filling a low spot in the lawn, 12 × 8 ft, averaging 5 in deep. 12 × 8 = 96 sq ft. 96 × (5 ÷ 12) = 40 cu ft. 40 ÷ 27 = 1.48 yd³. Add 15% = 1.70 yd³. Order 2 yards and cap the last few inches with topsoil.
Raising a 20 × 10 ft area by 6 inches for a shed. 200 sq ft × 0.5 = 100 cu ft = 3.70 yd³. Add 15% = 4.26 yd³, one load in a single-axle dump truck.
Backfilling a trench 40 ft long, 1 ft wide, 2 ft deep. 40 × 1 × 2 = 80 cu ft = 2.96 yd³. Add 15% = 3.41 yd³. If you are putting back the dirt you dug out, you will usually have enough. See the backfill calculator.
How many yards of dirt per square foot area
| Area | 2 in deep | 4 in deep | 6 in deep | 12 in deep |
|---|---|---|---|---|
| 100 sq ft | 0.62 yd³ | 1.23 yd³ | 1.85 yd³ | 3.70 yd³ |
| 250 sq ft | 1.54 yd³ | 3.09 yd³ | 4.63 yd³ | 9.26 yd³ |
| 500 sq ft | 3.09 yd³ | 6.17 yd³ | 9.26 yd³ | 18.52 yd³ |
| 1,000 sq ft | 6.17 yd³ | 12.35 yd³ | 18.52 yd³ | 37.04 yd³ |
These are measured volumes. Add your compaction allowance on top.
How many bags of dirt do I need?
Bagged soil is sold by volume, usually printed on the bag in cubic feet. Divide the cubic feet you need by the bag size:
| Bag size | Bags per cubic yard | Bags for 10 cu ft |
|---|---|---|
| 0.75 cu ft | 36 | 14 |
| 1 cu ft | 27 | 10 |
| 1.5 cu ft | 18 | 7 |
| 2 cu ft | 13.5 | 5 |
Bags make sense for small top-ups. For a cubic yard or more, get a bulk quote with delivery and compare. The fill dirt cost guide shows how to compare per yard, per ton and per load prices.
Common mistakes
- Forgetting to convert inches. 20 × 10 × 6 = 1,200 mixes feet and inches and is not cubic feet. Use 20 × 10 × 0.5 = 100 cubic feet.
- Measuring only the deepest point. Average several depths across a dip, or you will over-order.
- Skipping compaction. Loose dirt shrinks. A hole filled level with loose dirt will sink after the first heavy rain.
- Ordering by the ton without asking the weight. A ton of wet dirt is fewer yards than a ton of dry. See how much a yard of dirt weighs.
These methods give estimates. Ground is rarely perfectly flat, and soil weight swings with moisture, so check your numbers with the supplier and keep a small margin.
Questions people ask
- How many cubic feet are in a yard of dirt?
- 27. A cubic yard is a cube 3 feet long, 3 feet wide and 3 feet deep, and 3 × 3 × 3 = 27 cubic feet.
- How many yards of dirt do I need for 1,000 square feet?
- About 3.1 cubic yards per inch of depth. At 4 inches that is 12.3 yards, at 6 inches 18.5 yards, before any allowance for compaction.
- How many bags of dirt make a cubic yard?
- It depends on the bag size: 36 bags of 0.75 cubic feet, 27 bags of 1 cubic foot, 18 bags of 1.5 cubic feet, or about 14 bags of 2 cubic feet.
- Is it cheaper to buy dirt in bags or in bulk?
- For a few cubic feet, bags are simpler. Once you need more than roughly a cubic yard, bulk delivery is usually cheaper per yard, but compare a local bulk quote including delivery with the bag price before deciding.
- How do I measure an irregular area?
- Break it into rectangles, circles and triangles, work out each one, and add them. A triangle is half of base × height. For a curved bed, a rough rectangle a little smaller than the outer edges is close enough.