The first practical uroflowmeter was in use in 1946 and its use in children occurred in 1959 by Drake (J Urol 59:650–658, 1948). This has led to the introduction of uroflowmetry as a method of noninvasively evaluating children for voiding issues. The foundations of this methodology were set prior to the use of computers and advanced electronics relying on visual and analog data that makes it hard to create standardization in reading the studies. Much of the foundation in the field is based on expert opinion and there have been issues with repeatability and consistency in the reading of uroflow studies. This is primarily due to the lack of standardized normals in creating the shapes, and the patient selection is based on asymptomatic patients which are not necessarily normal voiders. The concept of the ideal voider or the perfect normal was introduced by Franco et al. in their publication “A quantitative approach to the interpretation of uroflowmetry in children” (Neurourol Urodyn 35:836–846, 2016). The ideal voider is defined as someone who voids with a bell curve on repeated flows, the bladder volume is less than 115% of EBC, and the PVR is less than 20 cc. This, along with the introduction of the flow index which utilizes the total bladder volume as the reference to measure the expected Qmax and Qavg, leads to a means of normalizing flow rates based on volume. Additional work demonstrating poor interrater reliability among the various shapes has led to a working group from the Society of Pediatric Urology to recommend the use of a second tier for cataloging flows based on whether the flow is smooth or fractionated. Utilizing this methodology which is rooted in sound thermodynamics and physical properties, we can develop a better way to report uroflows. This chapter outlines the physical science behind the foundations and then offers generous examples to help the reader apply this methodology.