The Unruh temperature, sometimes called the Davies–Unruh temperature, was derived separately by Paul Davies and William Unruh and is the effective temperature experienced by a uniformly accelerating detector in a vacuum field. It is given by
where  is the reduced Planck constant,  is the proper uniform acceleration,  is the speed of light, and  is the Boltzmann constant. Thus, for example, a proper acceleration of  corresponds approximately to a temperature of . Conversely, an acceleration of  corresponds to a temperature of .
The Unruh temperature has the same form as the Hawking temperature  with  denoting the surface gravity of a black hole, which was derived by Stephen Hawking in 1974. In the light of the equivalence principle, it is, therefore, sometimes called the Hawking–Unruh temperature.
Solving the Unruh temperature for the uniform acceleration, it can be expressed as
where  is Planck acceleration and  is Planck temperature.