Background <p>Sleeve gastrectomy has emerged as a leading bariatric procedure due to its effectiveness in inducing significant weight loss and improving obesity-related comorbidities. The calibration bougie size is a critical technical factor that influences outcomes, yet no universal consensus exists regarding optimal sizing.</p> Methods <p>A systematic review and network meta-analysis was conducted according to PRISMA guidelines. Electronic databases (PubMed, Embase, Cochrane Library, Web of Science) were searched for studies examining bougie size in sleeve gastrectomy published between January 2000 and September 2024. Primary outcomes included weight loss efficacy, complication rates, and patient satisfaction.</p> Results <p>Thirty-five studies with 13,450 patients were included. Bougie sizes ranged from 32 to 50 Fr, with most surgeons utilizing 34–40 Fr. Network meta-analysis demonstrated that smaller bougie sizes (32–36 Fr) were associated with greater excess weight loss (pooled mean difference: 6.7%, 95% CI: 3.2–10.2, <i>p</i> &lt; 0.001) but higher rates of strictures (OR: 2.14, 95% CI: 1.36–3.37, <i>p</i> = 0.001) and gastroesophageal reflux (OR: 1.76, 95% CI: 1.12–2.78, <i>p</i> = 0.015). Mid-range bougie sizes (36–40 Fr) showed intermediate results for both weight loss and complications. Patient-specific factors including baseline BMI, comorbidities, and anatomical variations significantly influenced outcomes, with bougie size having greater impact in patients with lower baseline BMI.</p> Conclusions <p>This network meta-analysis identifies that bougie size significantly impacts both weight loss and complication rates following sleeve gastrectomy. While mid-range bougie sizes (36–40 Fr) may balance weight loss efficacy and safety for many patients, bougie selection should be individualized based on patient characteristics, surgeon experience, and institutional protocols. Prospective studies are needed to establish evidence-based guidelines for personalized bougie size selection.</p>