This vaginal birth after cesarean (VBAC) success and risk calculator helps identify the mathematical chance of having a vaginal birth after cesarean. The VBAC calculator is based on the equation published in the article cited below. 

Grobman WA, et al "Development of a nomogram for prediction of vaginal birth after cesarean delivery," Obstetrics and Gynecology, volume 109, pages 806-12, 2007.