Cubic Feet Calculator
Measure in feet and inches; get cubic feet, gallons and bags.
Sources checked 9 November 2026
Cubic feet calculator
How to calculate cubic feet from feet and inches
Cubic footage, the volume of a space in cubic feet, is length × width × height, with every size in feet. Turn inches into feet first by dividing them by 12, multiply the three sizes, and the result is cubic feet. A 4 × 8 ft raised bed, 12 in deep is 8 × 4 × 1 = 32 cu ft. The steps below follow the sizes in the calculator above and change as you type.
Read the tape into feet
8′ 0″ = 8 ft. 4′ 0″ = 4 ft. 1′ 0″ = 1 ft.
Area times depth for each piece
- 8.00 × 4.00 = 32.00 sq ft; × 1.00 ft deep = 32.00 cu ft
Convert
32.00 ÷ 27 = 1.19 cu yd; 32.00 × 7.4805 = 239.38 US gallons
Bags: divide by the bag size, round up
32.00 cu ft ÷ 2 = 16.0, so 16 bags of 2 cu ft.
Cubic feet = length × width × depth
8.00 × 4.00 × 1.00 = 32.00 cu ft = 1.19 cu yd
All sizes in feet.
Square feet do not convert to cubic feet on their own: an area needs a depth. If you already know the square feet, multiply them by the depth in feet. A bed of 32 sq ft filled 12 in deep is the same 32 cu ft; the calculator takes a known area as one of its shapes.
Cubic feet from inches: divide by 1,728
When the measurements are in inches, multiply them for the volume in cubic inches and divide by 1,728, the cubic inches in one cubic foot (12 × 12 × 12). A planter box 36 in long, 12 in wide and 10 in deep holds 4,320 cu in, which is 2.5 cu ft or 18.7 US gallons.
So a cubic foot is not 12 inches: it is a cube 12 in on every side. The calculator reads inches and sixteenths in every size, so you can type 36 in as 0 ft 36 in or as 3 ft.
Find the volume of a cylinder, a ring or an L-shaped bed
For any shape, the volume is the area of its top times its height. Pick the shape of each piece in the calculator; it calculates the volume of each piece and adds them up.
Volume of a cylinder
3.1416 × (diameter ÷ 2)² × height. A round planter 24 in across and 18 in deep holds 4.71 cu ft, or 35.3 gallons. Measure across the top for the diameter; half of it is the radius.
Ring, half circle, triangle, trapezoid, oval and border
A ring is a circle with a hole, such as a bed around a tree; a border is a band around a rectangle, such as a gravel strip around a patio. The table gives every area formula; times the height, each is a volume.
| Shape | Formula | Example, feet | Area, sq ft |
|---|---|---|---|
| Rectangle | length × width | 12 × 10 | 120 |
| Triangle | base × height ÷ 2 | 10 × 6 ÷ 2 | 30 |
| Trapezoid | (top + bottom) ÷ 2 × height | (6 + 10) ÷ 2 × 8 | 64 |
| Circle | 3.1416 × radius² | 3.1416 × 5² | 78.54 |
| Half circle | 3.1416 × radius² ÷ 2 | 3.1416 × 5² ÷ 2 | 39.27 |
| Ring | 3.1416 × (outer radius² − inner radius²) | 3.1416 × (5² − 3²) | 50.27 |
| Oval | 3.1416 × half length × half width | 3.1416 × 6 × 4 | 75.4 |
| Border | outer area − inner area | 12 × 10 − 8 × 6 | 72 |
Sizes in feet give square feet. 3.1416 is π rounded; the calculator uses π in full.
Pieces added or taken away
An L-shaped bed is two rectangles added together. A tree well inside a bed is a circle taken away. Add a piece for each part, set it to Added or Taken away, and the total comes out net. A sphere is not one of the shapes: its volume is 4.1888 × (diameter ÷ 2)³.
Cubic feet to yards, gallons, liters and quarts
One cubic foot holds 7.48 US gallons or 28.32 liters, and 27 of them make a cubic yard. The calculator prints the calculated volume in all of these units under the total.
| One cubic foot | Equals |
|---|---|
| Cubic inches | 1,728 |
| US gallons | 7.4805 |
| Liters | 28.317 |
| Dry quarts (bag quarts) | 25.714 |
| Liquid quarts | 29.922 |
| Cubic yards | 0.037 |
| Cubic meters | 0.02832 |
Exact by definition: 1 ft = 0.3048 m, 1 US gallon = 231 cu in, 1 dry quart = 67.200625 cu in (NIST Handbook 44, Appendix C; NIST SP 811).
| Volume | Cubic feet |
|---|---|
| 5-gallon bucket, filled to 5 gal | 0.668 |
| Cubic yard | 27 |
| Cord of firewood, 4 × 4 × 8 ft | 128 |
Bucket: 5 × 231 cu in ÷ 1,728. Yard and cord: NIST Handbook 44, Appendix C.
Soil, gravel and mulch are sold by the cubic yard in bulk: the cubic yard calculator works out a bulk order with the extra.
Bags of soil for a raised bed or planter
Garden soil, potting mix and mulch are sold in bags marked in cubic feet or in quarts. To determine how much to buy, divide the cubic feet you need by the bag size and round up: the 4 × 8 ft raised bed, 12 in deep takes 22 bags of 1.5 cu ft or 16 bags of 2 cu ft.
| Bag | Cubic feet | Bags for 32 cu ft |
|---|---|---|
| 8 qt | 0.311 | 103 |
| 16 qt | 0.622 | 52 |
| 25 qt | 0.972 | 33 |
| 50 qt | 1.944 | 17 |
| 0.75 cu ft | 0.75 | 43 |
| 1 cu ft | 1 | 32 |
| 1.5 cu ft | 1.5 | 22 |
| 2 cu ft | 2 | 16 |
| 3 cu ft | 3 | 11 |
Sizes as sold: Miracle-Gro Potting Mix, Espoma Organic Potting Mix, Miracle-Gro Garden Soil All-Purpose, Miracle-Gro Organic Raised Bed & Garden Soil, Scotts Nature Scapes Color Enhanced Mulch, FoxFarm Ocean Forest Potting Soil, Kellogg Garden Organics. Quarts are dry quarts (67.2 cu in). Bags rounded up, no extra for settling.
The quarts printed on a bag are dry quarts, larger than the liquid quarts of a milk jug: one cubic foot is 25.71 dry quarts but 29.92 liquid ones, so a 50 qt bag holds 1.94 cu ft.
Utah State University Extension advises beds at least 6 to 12 in high for the roots of most vegetables.
Soil settles. UF/IFAS advises filling a raised bed to the very top, as the level may drop by about 2 in, then topping it off each season. Topping off the 4 × 8 ft bed by 2 in takes 5.33 cu ft, or 4 bags of 1.5 cu ft. Set the extra in the calculator if you want it in the first order.
Cubic feet calculator FAQ
How do I calculate cubic feet from dimensions?
Multiply length × width × height, all in feet. Turn inches into feet first (divide by 12). A 4 × 8 ft raised bed, 12 in deep is 32 cu ft.
Is a cubic foot 12 inches?
No. A cubic foot is a cube 12 in long, 12 in wide and 12 in high, which is 1,728 cubic inches.
How do I find the cubic feet of a cylinder?
3.1416 × (diameter ÷ 2)² × height, all in feet. A cylinder 24 in across and 18 in high is 4.71 cu ft.
How do I convert cubic feet to tons?
Multiply the cubic feet by the weight of one cubic foot of the material in pounds, then divide by 2,000. The weight depends on the material: water is about 62.4 lb per cubic foot (USGS, at 60 °F), so a cubic foot of water is 0.031 short tons. Soil and gravel vary with the material and how wet it is, so take the weight from your supplier.
How many gallons are in a cubic foot?
7.48 US gallons: a cubic foot is 1,728 cu in and a gallon is 231 cu in.
How many cubic feet are in a cubic yard?
27: a cubic yard is 3 ft × 3 ft × 3 ft.
How many quarts are in a cubic foot?
25.71 dry quarts, the quarts printed on bags of soil, or 29.92 liquid quarts.
How many cubic feet are in a 5-gallon bucket?
0.668 cu ft when it holds 5 gallons, so about one and a half bucketfuls make a cubic foot.
How many cubic feet are in a cord of wood?
128, by definition: a stack 4 ft high, 4 ft deep and 8 ft long.
How many bags of soil fill a 4 × 8 raised bed?
At 12 in deep the bed holds 32 cu ft: 22 bags of 1.5 cu ft or 16 bags of 2 cu ft. Keep about 4 more bags of 1.5 cu ft to top it off once it settles.
Related calculators
Sources
Unit definitions, bag sizes, bed heights and settling on this page come from these documents, checked 9 November 2026.
- NIST Special Publication 811, Guide for the Use of the International System of Units, 2008 edition
- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement
- Miracle-Gro Potting Mix product page
- Miracle-Gro Garden Soil All-Purpose product page
- Miracle-Gro Organic Raised Bed & Garden Soil product page
- Scotts Nature Scapes Color Enhanced Mulch product page
- Kellogg Garden Organics, Raised Bed & Potting Mix product page
- Espoma Organic Potting Mix product page
- FoxFarm Ocean Forest Potting Soil product page
- UF/IFAS Extension, Gardening in Raised Beds (ENH1211), revised February 2025
- Illinois Extension, Refreshing raised bed soil generates exceptional results, April 2021
- Utah State University Extension, Raised Bed Gardening, February 2012
- USGS Water Science School, Water Density