  Significant progress has recently been made in calculating muon stopping
sites using density functional theory. The technique aims to address two of the
most common criticisms of the muon-spin spectroscopy ($\mu^+$SR) technique,
namely, where in the sample does the muon stop, and what is its effect on its
local environment. We have designed and developed a program called MuFinder
that enables users to carry out these calculations through a simple graphical
user interface (GUI). The procedure for calculating muon sites by generating
initial muon positions, relaxing the structures, and then clustering and
analysing the resulting candidate sites, can be done entirely within the GUI.
The local magnetic field at the muon site can also be computed, allowing the
connection between the muon sites obtained and experiment to be made. MuFinder
will make these computations significantly more accessible to non-experts and
help to establish muon site calculations as a routine part of $\mu^+$SR
experiments.
