This paper presents a parametric study on the benefits and limitations of using 0.7 in. (18 mm) diameter strands in precast, pretensioned concrete bridge girders. A validated parametric study tool was used to design a variety of girders with 0.5, 0.6, and 0.7 in. (13, 15, and 18 mm) diameter strands using different span lengths, concrete release strengths, and transverse spacings. The most noticeable benefit of 0.7 in. (18 mm) diameter strands over 0.6 in. (15 mm) diameter strands was found to be a reduction of up to 35% in the number of strands.