  Stellar mass loss rates are an important input ingredient for stellar
evolution models since they determine stellar evolution parameters such as
stellar spin-down and increase in stellar luminosity through the lifetime of a
star. Due to the lack of direct observations of stellar winds from Sun-like
stars stellar X-ray luminosity and stellar level of activity are commonly used
as a proxy for estimating stellar mass loss rates. However, such an intuitive
activity --- mass loss rate relation is not well defined. In this paper, I
study the mass loss rate of the Sun as a function of its activity level. I
compare in-situ solar wind measurements with the solar activity level
represented by the solar X-ray flux. I find no clear dependency of the solar
mass flux on solar X-ray flux. Instead, the solar mass loss rate is scattered
around an average value of $2\cdot10^{-14}\;M_\odot\;yr^{-1}$. This
independency of the mass loss rate on level of activity can be explained by the
fact that the activity level is governed by the large modulations in the solar
close magnetic flux, while the mass loss rate is governed by the rather
constant open magnetic flux. I derive a simple expression for stellar mass loss
rates as a function of the stellar ambient weak magnetic field, the stellar
radius, the stellar escape velocity, and the average height of the Alfv\'en
surface. This expression predicts stellar mass loss rates of
$10^{-15}-10^{-12}\;M_\odot\;yr^{-1}$ for Sun-like stars.
