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 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.