To achieve an ideal colorimetric calibration for CMYK (cyan, magenta, yellow, and black) printers, we propose a novel CMYK determination technique under the restrictions of a colorimetric match, use of the entire color gamut, and a smooth gradation of each primary color. The algorithm proposed here includes the following steps: (1) obtain the two extreme conditions for CMYK combinations to be able to utilize the entire CMYK gamut, namely maximum black technique and minimum black technique; (2) determine an initial black amount that lies between the two conditions; (3) apply a smoothing technique for the black amount; and (4) determine the remaining colors, CMY, for colorimetric match. An iterative smoothing technique in a uniform color space is introduced to obtain visually "smoothed" black gradations. The gradation quallty for each primary color is evaluated with a hypothetical unstable printer. The smoothed CMYK technique eliminates sudden changes for each primary color, so that a printer using this technique becomes robust against a change of characteristic curves of the printer such as dot gain. Also, it is found that a CMYK combination using the technique is suitable for a lookup table and interpolation technique in practical conversions.