Outer faces and curved surfaces
Box Surface Area Calculator
Enter length, width and height, or choose a cube with equal sides. Calculate all six faces or leave out the top face.
Enter your measurements
Explore surface area calculators
Surface area of a rectangular prism
A closed rectangular box has three pairs of equal faces. Add them with A = 2(LW + LH + WH), where L is length, W width and H height.
Example: 4 ft × 3 ft × 2 ft
The top and bottom add 24 ft², the two long sides add 16 ft², and the two short sides add 12 ft². Total area = 52 ft², or approximately 4.83 m².
Cube surface area
Choose “Cube (all sides equal)” and enter one side length s. All six faces have area s², so a closed cube has A = 6s². For side length 3 ft, the result is 54 ft².
Open box without a top
Exclude one LW face: A = LW + 2LH + 2WH. The 4 ft × 3 ft × 2 ft example has 40 ft² with its top open. An open-top cube uses 5s².
“Lateral area” refers to the four side walls, with H as the vertical height. The selected result includes those walls plus either one or two horizontal faces.
Measure the surfaces you want to cover. Material overlaps, seams, cutouts and waste are separate from this geometric estimate. For capacity, use the box volume calculator.
Enter every length in the same unit. Results are rounded for display; calculations use unrounded values and the full precision of π.