The precise determination of the stellar effective temperature of solar type stars is of extreme importance for Astrophysics. We present an effective temperature calibration for FGK dwarf stars using line equivalent width ratios of spectral absorption lines. The ratios of spectral line equivalent width can be very sensitive to effective temperature variations for a well chosen combination of lines. We use the automatic code ARES to measure the equivalent width of several spectral lines, and use these to calibrate with the precise effective temperature derived from spectroscopy presented in a previous work.