Cuboid Surface Area Calculator
Find the total surface area of any rectangular box (cuboid) by entering its three dimensions. The calculator applies SA = 2(lw + lh + wh) and also shows the area of each pair of faces and the lateral surface area.
SA = 2(lw + lh + wh)
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Top/bottom face area (l × w)
8 × 5 = 40 - 2
Front/back face area (l × h)
8 × 3 = 24 - 3
Left/right face area (w × h)
5 × 3 = 15 - 4
Sum of three face pairs
40 + 24 + 15 = 79 - 5
Total surface area (×2 for all six faces)
2 × 79 = 158SA = 2(lw + lh + wh) — each pair appears twice on opposite sides.
How does this calculator work?
Total surface area of a cuboid = 2(lw + lh + wh), where l is length, w is width and h is height. The six faces come in three pairs: top/bottom (l×w), front/back (l×h) and left/right (w×h). Double each pair and add them together. Lateral SA (four walls only) = 2(lh + wh).
Formula
How this is calculated
A cuboid (rectangular box) has six rectangular faces that come in three identical pairs: two top-bottom faces of area l × w, two front-back faces of area l × h, and two left-right faces of area w × h. The total surface area is the sum of all six faces: SA = 2(lw + lh + wh). This formula appears in packaging design, painting estimation, gift-wrapping, and thermal insulation calculations.
The lateral surface area excludes the top and bottom faces and equals 2(lh + wh) = 2h(l + w), which represents just the four side walls — useful when calculating the paint or cladding needed for the walls of a box or a room without the floor and ceiling.
Units are arbitrary: enter centimetres for cm², metres for m², feet for ft², and so on. The formula is dimensionally consistent as long as all three measurements use the same unit. Rounding during measurement is the main source of error in real-world applications — the math itself is exact.
Frequently asked questions
Total surface area includes all six faces of the cuboid: 2(lw + lh + wh). Lateral surface area includes only the four side faces (excluding top and bottom): 2h(l + w). Use lateral SA when calculating wall area, cladding or wrapping with no top or bottom.
The formula works with any consistent unit. If you enter dimensions in centimetres, the surface area is in cm². In feet, it is in ft². Do not mix units — convert all three dimensions to the same unit first.
Yes. A cuboid, rectangular prism and rectangular parallelepiped are different names for the same shape: a 3-D solid with six rectangular faces, where each angle is 90°. A cube is the special case where all sides are equal.
TG we-Calculate Editorial Team. (2026). Cuboid Surface Area Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/cuboid-surface-area-calculator
TG we-Calculate Editorial Team. "Cuboid Surface Area Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/cuboid-surface-area-calculator.
TG we-Calculate Editorial Team, "Cuboid Surface Area Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/cuboid-surface-area-calculator
@misc{wecalculate_cuboid_surface_area_calculator, title = {Cuboid Surface Area Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/cuboid-surface-area-calculator}}, year = {2026}, note = {TG we-Calculate} }
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