The Fluxgate Magnetometers (FGM) on Magnetospheric Multiscale consist of a traditional Analog Fluxgate Magnetometer (AFG) and a Digital Fluxgate magnetometer (DFG). The dual magnetometers are operated as a single instrument providing a single intercalibrated data product. Range changes occur at different times on the two instruments so the gains checked each periapsis can be carried out unambiguously to apoapsis. Cross correlation of calibration parameters can separate causes of the any apparent calibration changes. Use of Electron Drift Instrument (EDI) to determine the field along the rotation axis allows accurate monitoring of the zero levels along the rotation axis. Prior to launch the magnetometers were calibrated at the Technical University, Braunschweig, except for the AFG magnetometers on MMS3 and MMS4, which were calibrated at UCLA. Both sets of sensors are operated for the entire MMS orbit, with slow survey (8 samples per second) outside of the Region of Interest (ROI), and fast survey (16 samples per second) inside the ROI. Within the ROI, burst mode data (128 samples per second) are also acquired. A detailed description of the MMS fluxgate magnetometers, including science objectives, instrument description, calibration, magnetic cleanliness program, and data flow can be found at http://link.springer.com/article/10.1007%2Fs11214-014-0057-3 (DOI 10.1007/s11214-014-0057-3). Additional information can also be found at http://www-spc.igpp.ucla.edu/ssc/mms (UCLA), and http://www.iwf.oeaw.ac.at/de/forschung/erdnaher-weltraum/mms/dfg (IWF, Graz). For the purpose of creating a unified FGM Level 2 data product, burst mode data is taken from DFG and survey mode data is taken from AFG. Because AFG and DFG are cross-calibrated on an orbit-averaged basis, small differences in offset may be observed between Level 2 burst and survey mode data. Consequently, any differences are within the error of the measurement. Based on preliminary analysis of the data, the absolute error within the Region of Interest (ROI) is estimated to be no more than 0.1 nT in the spin-plane, 0.15 nT along the spin-axis and 0.2 nT in total magnitude.