A calculation method for calculating a white balance correction value is disclosed. When an image capture device utilizes an auxiliary light to capture an image, the weightings of the image color impacted by the color temperature of each light source are obtained by the brightness-rate which is provided by the environment light and the flash, and then the weightings of the color temperatures of the two light sources are balanced to obtain a white balance correction value. At last, the white balance correction value is applied to correct the white balance of the image.