  We model the large-scale linear galaxy bias $b_g(x,z)$ as a function of
redshift $z$ and observed absolute magnitude threshold $x$ for broadband
continuum emission from the far infrared to ultra-violet, as well as for
prominent emission lines, such as the H$\alpha$, H$\beta$, Lya and [OII] lines.
The modelling relies on the semi-analytic galaxy formation model GALFORM, run
on the state-of-the-art $N$-body simulation SURFS with the Planck 2015
cosmology. We find that both the differential bias at observed absolute
magnitude $x$ and the cumulative bias for magnitudes brighter than $x$ can be
fitted with a five-parameter model: $b_g(x,z)=a + b(1+z)^e(1 +
\exp{[(x-c)d]})$. We also find that the bias for the continuum bands follows a
very similar form regardless of wavelength due to the mixing of star-forming
and quiescent galaxies in a magnitude limited survey. Differences in bias only
become apparent when an additional colour separation is included, which suggest
extensions to this work could look at different colours at fixed magnitude
limits. We test our fitting formula against observations, finding reasonable
agreement with some measurements within $1\sigma$ statistical uncertainties,
and highlighting areas of improvement. We provide the fitting parameters for
various continuum bands, emission lines and intrinsic galaxy properties,
enabling a quick estimation of the linear bias in any typical survey of
large-scale structure.
