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Visit-to-visit variability (VVV) in blood pressure (BP) has been linked to adverse cardiovascular outcomes, but the number of measurements needed for reliable assessment is unclear. This study aimed to determine the minimum number of systolic BP (SBP) readings required to quantify VVV and predict major adverse cardiovascular events (MACE) in patients with hypertension. We have conducted a multicenter retrospective cohort study using electronic health records of the Korea University Medical Center database. Overall, data from 4,480 patients with hypertension who had more than nine BP readings during a maximum period of 2 years were identified. This study used the coefficient of variation (CV) for analysis of variability and its correlation with MACE over a 3-year follow-up. The area under the receiver-operating characteristic curve (AUC) for MACE prediction plateaued at around 0.60 with five readings, indicating minimal gain with additional readings. The mean CV that best predicted the 3-year MACE for five SBP readings was 8.2. Patients with high SBP variability (CV > 8, based on five readings) had a hazard ratio of 1.89 (95% confidence interval, 1.48–2.41) for 3-year MACE, compared with those with low SBP variability. In multivariable analysis, high SBP variability remained an independent risk factor of MACE. To conclude, a minimum of five SBP readings appear sufficient to estimate visit-to-visit variability associated with cardiovascular risk in patients with hypertension. Assessment of SBP variability using routinely collected clinic measurements may complement conventional risk evaluation, although further validation in broader hypertensive populations is warranted.