How it’s calculated
A box (rectangular prism or cuboid) holds length × width × height. The surface area is the six faces added together, and the space diagonal runs corner to opposite corner.
Example: a 2 × 3 × 4 ft box holds 24 ft³ ≈ 679.6 L ≈ 179.5 US gal, has surface area 2(6 + 8 + 12) = 52 ft² and a space diagonal of √29 ≈ 5.39 ft.
Frequently asked questions
How do I calculate the volume of a box?
Multiply length × width × height using the same units. A 2 ft × 3 ft × 4 ft box is 24 cubic feet.
How many gallons are in a cubic foot?
About 7.48 US gallons. A US gallon is defined as 231 in³ and a cubic foot is 1,728 in³, so 1,728 ÷ 231 ≈ 7.4805.
How much cardboard do I need for a box?
The surface area output gives the area of all six faces. Add extra for flaps and overlaps.
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Sources
- Prealgebra 2e, 9.6 Solve Geometry Applications: Volume and Surface Area — OpenStax
- Cuboid — Wolfram MathWorld
- NIST Handbook 44, Appendix C: Units of Measurement — U.S. National Institute of Standards and Technology
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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