  We assess the systematic uncertainties in stellar evolutionary calculations
for low- to intermediate-mass, main-sequence stars. We compare published
stellar tracks from several different evolution codes with our own tracks
computed using the stellar codes STARS and MESA. In particular, we focus on
tracks of 1 and 3 solar masses at solar metallicity. We find that the spread in
the available 1 solar mass tracks (computed before the recent solar composition
revision by Asplund et al.) can be covered by tracks between 0.97-1.01 solar
masses computed with the STARS code. We assess some possible causes of the
origin of this uncertainty, including how the choice of input physics and the
solar constraints used to perform the solar calibration affect the tracks. We
find that for a 1 solar mass track, uncertainties of around 10% in the initial
hydrogen abundance and initial metallicity produce around a 2% error in mass.
For the 3 solar mass tracks, there is very little difference between the tracks
from the various different stellar codes. The main difference comes in the
extent of the main sequence, which we believe results from the different
choices of the implementation of convective overshooting in the core.
Uncertainties in the initial abundances lead to a 1-2% error in the mass
determination. These uncertainties cover only part of the total error budget,
which should also include uncertainties in the input physics (e.g., reaction
rates, opacities, convective models) and any missing physics (e.g., radiative
levitation, rotation, magnetic fields). Uncertainties in stellar surface
properties such as luminosity and effective temperature will further reduce the
accuracy of any potential mass determinations.
