Difference between the [Fe/H] calibrations from Terrien et al. (2015, T15), estimated for the M dwarfs from H-band relationships given by Newton et al. (2014) calibrations and [Fe/H] from this work. On the horizontal axis we show the [Fe/H] that we infer from our best fit BT-Settl model used in this work. The black full line represents the origin and the dashed black lines represent the error from the grid size of 0.1 dex.