INTRODUCTION: Determining limb length in gastric bypass procedures is a crucial step to ensure significant weight loss without risking malnutrition. This study investigated the effect of ex vivo training on the skills needed to determine limb lengths. MATERIALS AND METHODS: This was a single-center ex vivo training experiment in a teaching hospital in the Netherlands. We designed a training exercise with marked ropes in a laparoscopic trainer box. All ten surgical residents participated and practiced the skill of estimating limb length. Before and after the two-week period their results on a 150-centimeter limb length task were evaluated. RESULTS: Before training, 10 surgical residents estimated 150 centimeters of small bowel with an absolute deviation of 21% [range 9-30]. After the training experiment, the residents measured with 8% [2-20] deviation (P = .17). The 8 residents who trained sufficiently improved statistically significantly to an absolute deviation of 5% [2-17] (P = .012). Over 70% of the participants felt their skills had improved. CONCLUSIONS: With sufficient training, surgical residents' skills in measuring small bowel length improved when tested in an ex vivo model. Residents became more confident in their laparoscopic measurement skills. This ex vivo training model is a alternative and addition to on-site training.