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Background Ureteral stones pose a high economic and medical burden among Emergency Department (ED) admissions. Management strategies vary from expectant therapy to surgical interventions. Since predictors of ureteral spontaneous stone passage (SSP) are still not well understood, we sought to create a novel nomogram to guide management decisions. Methods Charts were retrospectively reviewed for patients who presented to our institution's ED with non-febrile renal colic and received a radiological diagnosis of ureteral stone ≤10 mm. Demographic, clinical, laboratory, and non-contrast CT data were collected. This novel nomogram incorporates the serum neutrophil-to-lymphocyte ratio (NLR) as a potential predictor of SSP. The model was derived from a multivariate logistic regression and was validated on a different cohort. A receiver operator characteristic (ROC) curve was constructed and the area under the curve (AUC) was computed. Results A total of 1186 patients presented to our ED between January 2010 and October 2018. We randomly divided our population into a derivation and validation cohort in one to five ratio. A stone size ≥ 7 mm was the strongest predictor of SSP failure; OR=9.47; 95%CI (6.03-14.88). Similarly, a NLR ≥ 3.14 had 2.17; (1.58-2.98) the odds of retained stone. SSP failure was also correlated with proximal position, severe hydronephrosis, and leukocyte esterase ≥ 75, p=0.02, p=0.05, and p=0.006, respectively. The model had an AUC of 0.804 (0.776-0.832). The nomogram was also used to compute the risk of SSP failure (AUC 0.769 (0.709 - 0.829). Conclusions Our novel nomogram can be used as a predictor for SSP and can be used clinically in decision making.