Rectangular Prism Calculator

Calculate volume, surface area, space diagonal and edge length for a rectangular prism

Your result will appear here.

About the Rectangular Prism Calculator

Rectangular Prism Calculator finds volume, surface area and related dimensions for a box-shaped solid with rectangular faces. It is useful for cartons, rooms, storage containers and construction quantities where length, width and height define the geometry.

The calculator assumes straight sides and right angles. Irregular containers, tapered shapes and rounded corners can have different actual volume.

How to Use the Rectangular Prism Calculator

  1. Enter length.
  2. Enter width.
  3. Enter height.
  4. Calculate volume or surface area and use internal dimensions for capacity or external dimensions for outside size.

How the Calculation Works

For a rectangular prism with length l, width w and height h, volume V = l×w×h. The three dimensions must first be expressed in compatible linear units, and the resulting unit is cubed because the calculation measures three-dimensional capacity or solid volume.

Total surface area A = 2(lw+lh+wh) because each of the three distinct rectangular face pairs appears twice. The space diagonal is d = √(l²+w²+h²), which gives the straight-line distance between opposite corners through the interior of the prism.

Worked example

Rectangular Prism Calculator Worked Example

Box 8 m × 5 m × 3 m

Volume = 8×5×3 = 120 m³. Surface area = 2×(8×5 + 8×3 + 5×3)=2×79=158 m².

Result guide

Understanding Your Rectangular Prism Calculator Result

Volume measures three-dimensional capacity, while surface area measures the total area of the six faces. They use cubic and square units respectively. If a box has wall thickness, calculate internal and external prisms separately rather than subtracting one dimension only. Thickness affects both opposing faces in each dimension, so internal length, width and height each decrease by twice the wall thickness before internal capacity is calculated.

Before you rely on the answer

Assumptions and Limitations

  • All faces are rectangular and meet at right angles.
  • Dimensions use the same unit before multiplication.
  • Internal versus external measurements match the intended result.

Practical tip

Using This Result in Practice

For packaging, calculate internal volume and external shipping dimensions separately. Wall thickness can make a meaningful difference when many boxes are stacked or freight is charged by dimensional size.

Related calculations

Useful Calculations to Continue With

If the object is not a rectangular prism, use the Volume Calculator to choose the appropriate shape.

If you need to compare surface area across several solids, use the Surface Area Calculator where appropriate.

Common questions

Rectangular Prism Calculator FAQ

What is rectangular prism volume?

Length×width×height.

What units does volume use?

Cubic units, such as m³ or ft³.

Should I use inside or outside dimensions?

Use inside dimensions for capacity and outside dimensions for external size.