  We present an algorithm developed to measure the fluxes of major meteor
showers as observed in NASA's All-Sky Fireball Network cameras. Measurements of
fluxes from the All-Sky cameras not only improve the Meteoroid Environment
Office's (MEO's) ability to provide accurate risk assessments from major
showers, but also allows the mass distribution of meteoroids within the shower
to be constrained. This algorithm accounts for the shower-specific and
event-specific exposure time and collecting area of the sky for nights where
sufficiently large samples of shower meteors ($\sim 30$ or more from the
shower) are observed. The fluxes derived from the All-Sky Fireball Network for
the 2015 Geminid, 2016 Perseid and Quadrantid, 2017 Orionid, and 2018 Leonid
shower peaks are calculated. All five of these shower fluxes show excellent
agreement with expectations from independent measurements at different mass and
luminosity limits. For four of these five showers, the measured mass indices
are significantly shallower than what is currently assumed by the NASA
Meteoroid Environment Office's (MEO's) annual meteor shower forecast. A direct
comparison between forecasted and measured fluxes at limiting masses of $\sim 1
\thinspace \mathrm{g}$ shows good agreement for the three showers for which the
observations took place near their peak activity.
