The minimum diameter for propagation of a detonation wave at a stable velocity. Critical diameter is affected by conditions of confinement, temperature, and pressure on the explosive.

It is strongly texture dependent, and is larger in cast than in pressed charges. Finely dispersed gas inclusions considerably reduce the critical diameter.

In the case of very insensitive materials- ammonium nitrate for example, the critical diameter may be very large. While in explosive products such as Dexs the critical diameter may be a cross-section as small as 1/64".