Math July 13, 2026 · 8 Min Read

Rectangular Prism Calculator – Guide & Formulas

Calculate the volume, diagonal length, and surface area of a rectangular prism (box) instantly with custom dimensions.

Find all parameters of a rectangular prism, cuboid, or standard cardboard box. Solves total capacity, surface area, and three-dimensional diagonal lengths.

Key Takeaway

Use the free Rectangular Prism Calculator to calculate the volume, diagonal length, and surface area of a rectangular prism (box) instantly with custom dimensions. Get instant results with step-by-step explanations.

How to Use the Rectangular Prism Calculator

  1. Enter the length, width, and height of the rectangular prism.
  2. Check the computed volume, total surface area, and space diagonal.
  3. Use this tool to design shipping packages, storage rooms, or aquarium capacities.

The Formula

V = length * width * height | A = 2*(l*w + l*h + w*h)

Variable Definitions

  • V: Volume of the rectangular prism
  • A: Total outer surface area
  • l, w, h: Length, width, and height dimensions

Shipping Box Capacity

A standard shipping box has dimensions of 12 inches long, 8 inches wide, and 10 inches high. Find its volume.

  1. Step 1: Set length = 12, width = 8, height = 10.
  2. Step 2: Multiply the three inputs: 12 * 8 * 10 = 960.
  3. Step 3: The box has a volume of 960 cubic inches.
  4. Step 4: Calculate surface area: 2 * (12*8 + 12*10 + 8*10) = 2 * (96 + 120 + 80) = 592 square inches.

Frequently Asked Questions

What is a space diagonal?

A space diagonal is the straight-line distance between two opposite corners of the prism, cutting through the center in three-dimensional space, solved with d = √(l² + w² + h²).

Is a cube a rectangular prism?

Yes. A cube is a special case of a rectangular prism where the length, width, and height are all perfectly equal.

How do you convert cuboid volume to liters?

If dimensions are in centimeters, divide the volume in cm³ (mL) by 1,000 to get the capacity in liters.