A method is described for calibrating a trichromatic halftone printing system in CIELAB colorimetric coordinates. The calibration method involves the use of three analytic equations rather than a LUT and interpolations. Calibration is done empirically by sending to the printing system a set of dot fraction vectors, [c m y]. CIELAB [L*a*b*] vectors are measured for each printed sample, and a statistical and algebraic analysis then leads to three algebraic equations for converting [L*a*b*] vectors to [c m y] vectors. The quality and efficiency of this calibration technique are discussed in comparison to the more common LUT technique with interpolations. Calibration quality was measured both as the average and the maximum value of CIELAB ΔE between the printed and the calculated [L*a*b*] vectors. The potential utility of the algebraic method of calibration is discussed in terms of the tradeoff between colorimetric accuracy, computational speed, and the ease of performing the calibration.