Introduction Currently, the need for additional myofascial release (AMR) in addition to retromuscular dissection during open Rives–Stoppa hernia repair is determined intraoperatively based on the discretion of the surgeon. We developed a novel method to objectively predict the need for AMR preoperatively using computed tomography (CT)-measured rectus width to hernia width ratio (RDR). Methods A retrospective chart review of all patients who underwent open retro-muscular mesh repair of midline ventral hernia between August 1, 2007 and February 1, 2018, who had a preoperative CT scan within 1 year prior to their operation. The primary endpoint was the ability of the defect ratio to predict the need for AMR in pursuit of fascial closure. The secondary endpoint was the ability of Component Separation Index (CSI) to predict the need for AMR to obtain fascial closure. Results Of 342 patients, 208 repaired with rectus abdominis release alone (RM group), while 134 required AMR (RM + group). An RDR of > 1.34 on area under the curve analysis predicted the need for AMR with 77.6% accuracy. There was a linear decrease in the need for AMR with increasing RDR: RDR < 1 required AMR in 78.8% of cases, RDR 1.1–1.49 in 52%, RDR 1.5–1.99 in 32.1%, and RDR > 2 in just 10.8%. Similarly, CSI > 0.146 predicted the need for AMR with 76.3% accuracy on area under the curve analysis. Conclusion The RDR is a practical and reliable tool to predict the ability to close the defect during open Rives–Stoppa ventral hernia repair without AMR. An RDR of > 2 portends fascial closure with rectus abdominis myofascial release alone in 90% of cases.