There is a lack of consensus in the definition of stone-free rate (SFR) after ureteric or renal stone surgery. We propose a simple classification to define levels of SFR post-treatment.

Based on the follow-up modality, the suffix U (USS), C (CT) or X (X-ray) should be included with the SFR level (Table 1). This simple proposal will not only clarify the size of the stone post-treatment, but also the follow-up modality used to determine it.

Table 1 Definition of stone-free rate (SFR) level