Rectangular Prism Calculator — Volume & Surface Area
A rectangular prism (also called a cuboid or box) has three pairs of identical rectangular faces. Enter the length, width and height to get the volume, surface area, space diagonal and all three face diagonals instantly.
Volume = length × width × height
60
volume- 1
Base area
l × w = 5 × 4 = 20 - 2
Volume
base area × h = 20 × 3 = 60
How does this calculator work?
Rectangular prism: Volume = l × w × h; Surface area = 2(lw + lh + wh); Space diagonal = √(l² + w² + h²). Enter all three dimensions in any consistent unit; volume comes out in cubic units, surface area in square units. A cube is the special case where l = w = h.
Formula
How this is calculated
A rectangular prism is a 3-D solid in which all faces are rectangles and all angles are right angles. Its three distinct dimensions are length (l), width (w), and height (h). The volume — the amount of space it encloses — is simply the product of all three: V = l × w × h.
The surface area counts the total area of all six faces: two l×w faces (top and bottom), two l×h faces (front and back), and two w×h faces (left and right), giving SA = 2(lw + lh + wh). The space diagonal connects two opposite corners through the interior: d = √(l² + w² + h²), derived by applying the Pythagorean theorem twice. Each of the three pairs of faces also has its own face diagonal: √(l²+w²), √(l²+h²), and √(w²+h²).
Use any consistent unit (cm, m, inches, feet) — the volume comes out in cubic units and the surface area in square units of the same measure.
Frequently asked questions
A cube is a special rectangular prism where all three dimensions are equal (l = w = h). Every cube is a rectangular prism, but not every rectangular prism is a cube.
Use SA = 2(lw + lh + wh). This gives the total outer surface, typically in square centimetres or square inches. Add 10–15% extra for practical purposes like overlaps in wrapping paper.
The space diagonal is the longest straight-line distance inside the box — useful for checking whether a long object (a fishing rod, a piece of timber) fits inside a shipping container or room, since it is longer than any edge or face diagonal.
Also known as
TG we-Calculate Editorial Team. (2026). Rectangular Prism Calculator — Volume & Surface Area [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/rectangular-prism-calculator
TG we-Calculate Editorial Team. "Rectangular Prism Calculator — Volume & Surface Area." TG we-Calculate. 2026. https://we-calculate.com/calculator/rectangular-prism-calculator.
TG we-Calculate Editorial Team, "Rectangular Prism Calculator — Volume & Surface Area," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/rectangular-prism-calculator
@misc{wecalculate_rectangular_prism_calculator, title = {Rectangular Prism Calculator — Volume & Surface Area}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/rectangular-prism-calculator}}, year = {2026}, note = {TG we-Calculate} }
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