  Bolometric luminosity is a basic physical parameter that is widely used in
the study of blazars. Due to the lack of simultaneous full wavelength data,
several estimators of the bolometric luminosity are being used in practice. In
this paper, we study and evaluate the reliability and significance of six
estimators, the $5GHz$ luminosity, the 1keV luminosity, the $\gamma$-ray
luminosity, the $5GHz$ luminosity+the 1keV luminosity, the $5GHz$
luminosity+the $\gamma$-ray luminosity and the 1keV luminosity+the $\gamma$-ray
luminosity, by analyzing the linear correlations between the integrated
bolometric luminosity and them. Our main results are as follows. (i) All the
six estimators are reliable in the sense that they are all significant
correlated with the bolometric luminosity. (ii) Ranking from the higher
significance of the reliability to lower one the six estimators are the the
$5GHz$ luminosity+the $\gamma$-ray luminosity, the 1keV luminosity+the
$\gamma$-ray luminosity, $\gamma$-ray luminosity, the $5GHz$ luminosity+the
1keV luminosity, the $5GHz$ luminosity and the 1keV luminosity. (iii) We
suggest that the bolometric luminosity can be well estimated by the
$\gamma$-ray luminosity using the best linear equation that given in this paper
for Fermi FSRQs. (iv) According to the linear regressions obtained in the
analysis, we provide calibration for each estimator.
