What is a cubic yard?
A cubic yard is the space inside a cube 3 feet long, 3 feet wide and 3 feet high, which is 27 cubic feet. Dirt, topsoil, mulch, gravel and ready-mix concrete are sold in bulk by the cubic yard, often just called a "yard".
Source NIST Handbook 44 (2026) · Appendix C, General Tables of Units of Measurement ↗
How to calculate cubic yards
Here it is with your numbers:
- Change 3 in to feet: 0.25 ft.
- Multiply the length, width and depth: 20 × 10 × 0.25 = 50 cu ft.
- Divide by 27 to get cubic yards: 50 ÷ 27 = 1.8519 cu yd.
- Round to two decimal places: 1.85 cu yd.
It means you need 1.85 cubic yards. Order 2 cubic yards so you don't run short.
Change every measurement to feet first: divide inches by 12, so 3 inches deep is 0.25 ft. Multiply length, width and depth to get cubic feet, then divide by 27. For a round bed, use the distance all the way across and halve it.
Source Common Core State Standards · Grade 5, volume of a box (5.MD.C.5.b) ↗Common Core State Standards · Grade 8, volume of a cylinder (8.G.C.9) ↗
Cubic yards for 1,000 square feet
How much you need for every 1,000 square feet (for example 40 ft × 25 ft) at common depths.
FAQs
How many cubic feet are in a cubic yard?
27 cubic feet. A cubic yard is a cube 3 feet on each side, and 3 × 3 × 3 = 27. To turn cubic feet into cubic yards, divide by 27.
Source NIST Handbook 44 (2026) · Appendix C, General Tables of Units of Measurement ↗
How big is a cubic yard?
A cube 3 feet long, 3 feet wide and 3 feet high, about 0.76 cubic meters. Spread 3 inches deep, one cubic yard covers 108 square feet.
How many cubic yards is 1,000 square feet?
It depends on the depth. At 3 inches deep, 1,000 square feet is 9.26 cubic yards (1,000 × 0.25 ÷ 27). At 2 inches it is 6.17, and at 4 inches 12.35.
How many gallons are in a cubic yard?
About 201.97 US gallons. A cubic yard is 46,656 cubic inches and a gallon is 231 cubic inches, so 46,656 ÷ 231 = 201.97.
Sources
- NIST Handbook 44 (2026): Appendix C, General Tables of Units of Measurement
- Common Core State Standards: Grade 5, volume of a box (5.MD.C.5.b)
- Common Core State Standards: Grade 8, volume of a cylinder (8.G.C.9)