Cuboid Space Diagonal

How to use this calculator

1. Enter length in cm.
2. Enter width in cm.
3. Enter height in cm.
4. Select Calculate and keep the output unit with the answer.

Before you use the answer

Start with a dimensioned sketch and label the units beside every measurement. Distinguish the outer edge from an internal opening, and distinguish a radius from a diameter. A geometric model is most useful when the shape actually matches the assumptions in the formula.

This is longer than any single face diagonal and is not an edge length.

Does it save my inputs?

No calculation history is stored by this website. The calculator works locally in your browser. See the privacy policy for hosting and contact details.

Why might a result be approximate?

Measurement uncertainty, ideal-model assumptions and floating-point rounding can all matter. Displaying more digits does not improve the original measurement.