Vacuum fluctuations of the gravitational field lead to fluctuations in the measured length of an interferometer, such as LIGO. It has been suggested that due to some exotic quantum gravity effects, these fluctuations could be large enough to be observed. I will give two calculations using standard perturbative gravity viewed as an effective field theory, one purely geometrical and one with an explicit model of a realistic detector. To the surprise of no one, both of these predict unobservably small fluctuations, in line with simple scaling arguments. The precise calculational framework is interesting and involves a few subtleties, which is the real focus of the talk.