Cubic Feet Calculator
This cubic feet calculator multiplies length × width × height, all in feet. A box 3 ft × 2 ft × 18 in holds 3 × 2 × 1.5 = 9 cubic feet, which is 0.33 cubic yards or 67 gallons. If you measured in inches, multiply the three numbers and divide by 1,728.
Example: 3 × 2 ft at 18 in
9 cubic feet
- 0.33 cu yd
- 67 gallons
0.33 yd³
How to calculate cubic feet
Multiply length × width × height with all three in feet. A box 3 ft long, 2 ft wide and 18 inches tall is 3 × 2 × 1.5 = 9 cubic feet, since 18 inches is 1.5 feet. The calculator takes rectangles, circles and any floor area you already know. Lengths take feet and inches; the Height box takes inches, so a box 2 ft tall goes in as 24. For a set of planters, or a bed with an extension, use “Add another area” and it adds them up.
An easy slip when working by hand is multiplying feet by inches: 3 × 2 × 18 gives 108, twelve times the real 9 cubic feet. If an answer looks far too big, check that the height went in as feet.
If you measured everything in inches, multiply the three numbers and divide by 1,728, the number of cubic inches in a cubic foot (12 × 12 × 12). The same box is 36 × 24 × 18 = 15,552 cubic inches, and 15,552 ÷ 1,728 = 9.
With mixed units, turn the inches into feet first by dividing by 12. A raised bed 8 ft long and 4 ft wide, filled 11 inches deep, uses 11 ÷ 12 = 0.92 ft for the height:
- Area: 8 ft × 4 ft = 32 sq ft; × 11 in deep = 29.3 cu ft.
- 29.3 cu ft ÷ 27 = 1.09 cubic yards.
- Rounded up to the next 0.5 cubic yard: order 1.5 cubic yards.
Before any extra, that’s 15 bags of 2 cu ft (29.3 ÷ 2 = 14.7, rounded up) or 40 bags of the 0.75 cu ft size.
When you already know the floor area, from a plan or a product listing, pick “Known area” and enter the square feet. By hand, multiply the square feet by the height in feet: 50 sq ft filled 6 inches deep is 50 × 0.5 = 25 cubic feet.
Cubic feet of a cylinder or round planter
A round pot, tub or tube is a cylinder, and its volume is π × radius² × height, where the radius is half the distance across. Pick the circle shape in the calculator and enter the diameter; it halves it for you.
- Area: π × (2 ft ÷ 2)² = 3.14 sq ft; × 18 in deep = 4.71 cu ft.
- 4.71 cu ft ÷ 27 = 0.17 cubic yards.
- Rounded up to the next 0.5 cubic yard: order 0.5 cubic yards.
That planter holds about 35 gallons, or 3 bags of 2 cu ft (4.71 ÷ 2 = 2.36, rounded up). Measure across the inside of the rim. A pot that narrows toward the bottom holds less than a cylinder as wide as its top, so treat the result as the most it could take. In inches the same planter is π × 12² × 18 = 8,143 cubic inches, and 8,143 ÷ 1,728 gives the same 4.71 cubic feet. A post hole is a cylinder too; the fence post concrete calculator turns holes into bags of concrete.
Cubic feet to cubic yards, gallons and liters
Bulk soil, mulch and gravel are sold by the cubic yard, which is 27 cubic feet, so divide cubic feet by 27. For water, use gallons. A US gallon is 231 cubic inches, so a cubic foot holds 1,728 ÷ 231 = 7.48 gallons. With the foot defined as exactly 0.3048 meters, a cubic foot is 28.32 liters and a cubic meter is 35.31 cubic feet. To go the other way, divide gallons by 7.48: a 100-gallon tank holds 13.4 cubic feet.
| Cubic feet | Cubic yards | Gallons | Liters |
|---|---|---|---|
| 1 | 0.04 | 7.48 | 28.3 |
| 2 | 0.07 | 15 | 56.6 |
| 5 | 0.19 | 37.4 | 142 |
| 9 | 0.33 | 67.3 | 255 |
| 27 | 1 | 202 | 765 |
| 100 | 3.7 | 748 | 2,832 |
The cubic feet to cubic yards converter does the yard conversion on its own, and the cubic yard calculator starts from yards if that’s how your supplier sells.
How many bags of soil or mulch fill it
Divide the cubic feet by the bag size and round up. Bag sizes vary by brand: Scotts Premium Topsoil comes in a 0.75 cu ft bag, Timberline topsoil in a 1 cu ft bag, Miracle-Gro Garden Soil All Purpose in 0.75, 1, 1.5 and 2 cu ft, and Scotts Nature Scapes mulch in 1.5 and 2 cu ft. One cubic yard takes 36 of the 0.75 cu ft bags, 27 of the 1 cu ft, 18 of the 1.5 cu ft or 13.5 of the 2 cu ft.
Choose Topsoil or Hardwood mulch in the calculator to see bag counts. It adds 5% extra for spillage, which you can change. The table below does the same for raised beds of several sizes with the 0.75 cu ft topsoil bag. Under each count are the bulk order in cubic yards and the weight of dry soil. A 4 × 12 ft bed 24 inches deep takes 135 of those bags, so price that one as a bulk delivery too.
| Area | 6 in deep | 12 in deep | 18 in deep | 24 in deep |
|---|---|---|---|---|
| 4 × 4 ft, 16 sq ft | 12 bags , 0.5 yd³ · 0.3–0.4 t | 23 bags , 1 yd³ · 0.6–0.8 t | 34 bags , 1 yd³ · 0.9–1.3 t | 45 bags , 1.5 yd³ · 1.2–1.7 t |
| 3 × 6 ft, 18 sq ft | 13 bags , 0.5 yd³ · 0.3–0.5 t | 26 bags , 1 yd³ · 0.6–0.9 t | 38 bags , 1.5 yd³ · 1–1.4 t | 51 bags , 1.5 yd³ · 1.3–1.9 t |
| 4 × 6 ft, 24 sq ft | 17 bags , 0.5 yd³ · 0.4–0.6 t | 34 bags , 1 yd³ · 0.9–1.3 t | 51 bags , 1.5 yd³ · 1.3–1.9 t | 68 bags , 2 yd³ · 1.7–2.5 t |
| 4 × 8 ft, 32 sq ft | 23 bags , 1 yd³ · 0.6–0.8 t | 45 bags , 1.5 yd³ · 1.2–1.7 t | 68 bags , 2 yd³ · 1.7–2.5 t | 90 bags , 2.5 yd³ · 2.3–3.4 t |
| 4 × 12 ft, 48 sq ft | 34 bags , 1 yd³ · 0.9–1.3 t | 68 bags , 2 yd³ · 1.7–2.5 t | 101 bags , 3 yd³ · 2.6–3.8 t | 135 bags , 4 yd³ · 3.5–5 t |
Includes 5% extra, rounded up to the next half cubic yard, as the calculator does. Tons (t) span the sourced density range. Bags are 0.75 cu ft bags.
Mulch goes on in a thinner layer. The University of Florida’s Florida-Friendly Landscaping program recommends 2 to 3 inches for beds. Mulching a 4 × 8 ft bed 3 inches deep takes 32 × 0.25 = 8 cubic feet, or 4 bags of 2 cu ft before extra.
Cubic feet for yard projects
- For raised beds and planters, measure inside the frame and use the depth you’ll fill to rather than the height of the boards.
- A 5 × 5 ft sandbox filled 6 inches deep holds 12.5 cubic feet, or 0.46 cubic yards. Sand is heavy, so run that volume through the cubic yard calculator with sand selected to see the weight before you load a car with bags.
- A 6 × 4 ft pond 2 ft deep with straight sides holds 48 cubic feet, or 359 gallons. Sloped sides and planting shelves hold less, so treat the box figure as the upper limit for a pond or water feature.
- For a truck or trailer bed, multiply the inside length and width by the height you’ll load to. Ram lists 61.5 cu ft for the 2026 Ram 1500’s 6′4″ box, about 2.28 cubic yards. With soil, weight runs out first: at the Tradesman’s 2,360 lb payload, one trip carries about 0.88–1.27 cubic yards of dry topsoil.
- A concrete form is a box too. A 3 × 3 ft pad 4 inches thick is 3 cubic feet, and Quikrete’s 80 lb bag of concrete mix yields 0.6 cu ft, so the pad takes 5 bags before extra. The concrete calculator adds the extra and handles footings, columns and steps.
Questions people ask
How do you calculate cubic feet?
Measure the length, width and height in feet and multiply them. A box 3 ft long, 2 ft wide and 18 inches tall is 3 × 2 × 1.5 = 9 cubic feet, because 18 inches is 1.5 feet. For a round container, use π × radius² × height instead.
How do I calculate cubic feet from inches?
Multiply length × width × height in inches, then divide by 1,728, the number of cubic inches in a cubic foot (12 × 12 × 12). A box 36 × 24 × 18 inches is 15,552 cubic inches, and 15,552 ÷ 1,728 = 9 cubic feet.
How many cubic feet are in a cubic yard?
27. A cubic yard is a cube 3 ft on each side, and 3 × 3 × 3 = 27. To turn cubic feet into cubic yards, divide by 27: 9 cubic feet is 0.33 cubic yards, and 54 cubic feet is 2.
How many gallons are in a cubic foot?
7.48 US gallons. A US gallon is defined as 231 cubic inches and a cubic foot is 1,728 cubic inches, so 1,728 ÷ 231 = 7.48. A cubic foot is also 28.32 liters, which means a 9 cubic foot box holds 67 gallons, or 255 liters, of water.
How do you find the cubic feet of a cylinder?
Multiply π (3.14) by the radius squared and then by the height, all in feet. The radius is half the distance across. A planter 2 ft across and 18 inches deep is 3.14 × 1 × 1 × 1.5 = 4.71 cubic feet, about 35 gallons.
How many cubic feet is a bag of soil?
It depends on the brand and product. Scotts Premium Topsoil comes in a 0.75 cu ft bag, Timberline topsoil in a 1 cu ft bag, and Miracle-Gro Garden Soil All Purpose in 0.75, 1, 1.5 and 2 cu ft sizes. Scotts Nature Scapes mulch comes in 1.5 and 2 cu ft bags. Divide your cubic feet by the bag size and round up.
How many bags of soil do I need for a 4x8 raised bed?
A 4 × 8 ft bed filled 12 inches deep holds 32 cubic feet: 16 bags of 2 cu ft, 32 bags of 1 cu ft or 43 bags of 0.75 cu ft. Filled 11 inches deep it holds 29.3 cubic feet, or 15 bags of 2 cu ft. With topsoil picked, the calculator adds 5% extra, which makes the 12-inch bed 45 bags of 0.75 cu ft.
Sources
- University of Florida IFAS Extension, Florida-Friendly Landscaping Program, Florida-Friendly Landscaping Principle 4 guidance (Mulch). Accessed Oct 19, 2026.
- USDA Natural Resources Conservation Service, Soil Health - Bulk Density (Soil Health Educators Guide sheet). Accessed Oct 19, 2026.
- South Dakota State University Extension (H. Klopp, A. Bly; updated 2023-09-22), Bulk Density is an Indicator of Soil Health. Accessed Oct 19, 2026.
- Ottr Landscape Supply (Boston, MA), Bulk Landscape Material Weight Guide: Dirt, Gravel, Mulch & More. Accessed Oct 19, 2026.
- ScottsMiracle-Gro, Scotts Premium Topsoil - 0.75 CF (product 7113075). Accessed Oct 19, 2026.
- Do it Best (retailer listing), Timberline 1 Cu. Ft. All-Purpose Top Soil (item 701263). Accessed Oct 19, 2026.
- USDA Natural Resources Conservation Service, National Engineering Handbook Part 637, Chapter 2 Composting (210-VI-NEH, Amend. 40, Nov 2010), Table 2A-1. Accessed Oct 19, 2026.
- Roseville Landscape Material Supply (Roseville, CA), Landscape Materials Calculator - Material Weight and Coverage Reference. Accessed Oct 19, 2026.
- Scotts Miracle-Gro, Scotts Nature Scapes Color Enhanced Mulch 2 cu. ft.. Accessed Oct 19, 2026.
- Scotts Miracle-Gro, Scotts Nature Scapes Color Enhanced Mulch 1.5 cu. ft.. Accessed Oct 19, 2026.
- National Institute of Standards and Technology (NIST), NIST Handbook 44 (2024), Appendix C: General Tables of Units of Measurement. Accessed Oct 19, 2026.
- Ram Trucks (Stellantis), 2026 Ram 1500 Specs (Tradesman 4x2 Quad Cab 6'4" box). Accessed Oct 19, 2026.
- The Quikrete Companies, LLC, QUIKRETE Concrete Mix (No. 1101) Data Sheet, revised October 2022. Accessed Oct 19, 2026.
- ScottsMiracle-Gro, Miracle-Gro Garden Soil All Purpose (75052430). Accessed Oct 19, 2026.