  The SKA will be the largest radio astronomy observatory ever built, providing
unprecedented sensitivity over a very broad frequency (50 MHz to 15.3 GHz). The
SKA-Low (50 - 350 MHz), will be built at the MRO in Western Australia. It will
consist of 512 stations each composed of 256 dual-polarised antennas, and the
sensitivity of an individual station is pivotal to the performance of the
entire SKA-Low telescope. The answer to the question in the title is, it
depends. The sensitivity of a low frequency array, such as an SKA-Low station,
depends strongly on the pointing direction of the digitally formed station beam
and the local sidereal time (LST), and is different for the two orthogonal
polarisations of the antennas. The accurate prediction of the SKA-Low
sensitivity in an arbitrary direction in the sky is crucial for future
observation planning. We present here a sensitivity calculator for the SKA-Low
radio telescope, using a database of pre-computed sensitivity values for two
realisations of an SKA-Low station architecture. One realisation uses the
log-periodic antennas selected for SKA-Low. The second uses a known benchmark,
in the form of the bowtie dipoles of the MWA. Data collected by both stations
(deployed at the MRO in 2019) were used to measure their sensitivity at
selected frequencies and over at least 24 h intervals, and were compared to the
predictions described in this paper. The sensitivity values stored in the
SQLite database were pre-computed for the X, Y and Stokes I polarisations in 10
MHz frequency steps, 0.5 hour LST intervals, and 5 degree resolution in
pointing directions. The database allows users to estimate the sensitivity of
SKA-Low for their favourite object using interactive web-based or command line
interface, which can also calculate the sensitivity for arbitrary pointing
directions, frequencies, and times without interpolations.
