  We provide the C++ tool BSMPT for calculating the strength of the electroweak
phase transition in extended Higgs sectors. This relies on the loop-corrected
effective potential at finite temperature including daisy resummation of the
bosonic masses. The program allows to compute the vacuum expectation value
(VEV) $v$ of the potential as a function of the temperature, and in particular
the critical VEV $v_c$ at the temperature $T_c$ where the phase transition
takes place. In addition, the loop-corrected trilinear Higgs self-couplings are
provided. We apply an 'on-shell' renormalization scheme in the sense that the
loop-corrected masses and mixing angles are required to be equal to their
tree-level input values. This allows for efficient scans in the parameter space
of the models. The models implemented so far are the CP-conserving and the
CP-violating 2-Higgs-Doublet Models (2HDM) and the Next-to-Minimal 2HDM
(N2HDM). The program structure is such that the user can easily implement
further models. Our tool can be used for the investigation of electroweak
baryogenesis in models with extended Higgs sectors and the related Higgs
self-couplings. The combination with parameter scans in the respective models
allows to study the impact on collider phenomenology and to make a link between
collider phenomenology and cosmology. The program package can be downloaded at:
https://github.com/phbasler/BSMPT.
