Rectangular Prism Calculator
Calculate the volume, total and lateral surface area, space diagonal, and base measurements of a rectangular prism (box) from length, width, and height.
Everyday Uses
Shipping and storage
Box volume tells you what fits — for moving, mailing rates, and storage units.
Aquarium sizing
Tank volume in liters or gallons determines fish stocking and heater size.
Room and material math
Concrete pours, soil for raised beds, air volume for HVAC — all box math.
Wrapping and painting
Surface area tells you how much paper, paint, or laminate covers the box.
Frequently Asked Questions
How do you find the volume of a rectangular prism?
V = length × width × height. A box measuring 8 × 5 × 3 has a volume of 120 cubic units. Volume is always expressed in cubic units (cm³, m³, ft³) because it fills three dimensions.
How do you find the surface area of a rectangular prism?
SA = 2(lw + lh + wh) — the box has three pairs of identical rectangular faces. For 8 × 5 × 3: SA = 2(40 + 24 + 15) = 158 square units. Lateral surface area (walls only, no top/bottom) is 2(l + w) × h.
What is the diagonal of a rectangular prism?
The space diagonal runs between opposite corners through the inside of the box: d = √(l² + w² + h²), the 3D Pythagorean theorem. For 8 × 5 × 3: d = √98 ≈ 9.90. Useful for checking whether a long object fits inside a box or room.
What is the difference between a rectangular prism, cuboid, and cube?
They describe the same family: a rectangular prism (US term) or cuboid (UK term) is a box with six rectangular faces. A cube is the special case where length = width = height, making all six faces identical squares.