Owing to a high amount of stress, seam failure in workwear fabrics makes the fabric unsuitable although the fabric strength is high. It is therefore important to predict the seam strength to ascertain the performance of the garments during use and determine the required thread strength to match the required seam strength. An assembly is composed of a sewing thread and a fabric. The thread forming the seam undergoes several stresses during its passage from the sewing machine to the formation of the loop and when wearing the garment: these are mechanical stresses. Therefore, it is necessary to evaluate the strength of the seam. But, in the bibliography, most researchers have studied the strength of the seam concerning a single type of stitch. This work aimed to examine the seam's strength from the resistance to the loop of the thread for all types of stitches. In all of the earlier predictive equations, seam strength is predicted from thread loop strength with some multiplicative factors. The thread loop strength is measured without considering the stitch type. During the sewing process, threads loop differently from one stitch to another, therefore, the standard thread loop strength becomes unfit to predict the seam strength. In this paper, the effects of loop thread length and configuration are studied on thread loop strength and seam strength. The seam strengths predicted from the loop strength before and after considering the new loop configurations and the real seam strength are compared. So, new clamps for loop strength are configured and carried out. It is observed that there is a closer match between experimental and predicted seam strength with new loop configurations. The loop configuration has a significant effect on the thread loop strength and improves the accuracy of seam-strength prediction.