  We present the simulator we developed for the Wide Field Monitor (WFM) aboard
the Large Observatory For X-ray Timing (LOFT) mission, one of the four ESA M3
candidate missions considered for launch in the 2022-2024 timeframe. The WFM is
designed to cover a large FoV in the same bandpass as the Large Area Detector
(LAD, almost 50% of its accessible sky in the energy range 2-50 keV), in order
to trigger follow-up observations with the LAD for the most interesting
sources. Moreover, its design would allow to detect transient events with
fluxes down to a few mCrab in 1-day exposure, for which good spectral and
timing resolution would be also available (about 300 eV FWHM and 10 {\mu}s,
respectively). In order to investigate possible WFM configurations satisfying
these scientific requirements and assess the instrument performance, an
end-to-end WFM simulator has been developed. We can reproduce a typical
astrophysical observation, taking into account both mask and detector physical
properties. We will discuss the WFM simulator architecture and the derived
instrumental response.
