Automatic milking system (AMS) recommendations for stocking density are based on company guidelines rather than empirically derived results. Our objectives were to evaluate how: a) hourly AMS visits varied with occupation rate (total h the AMS was available, minus time spent on other activities) and b) fat- and protein-corrected milk (FPCM) varied with stocking density (daily number of cows milked by an AMS). A retrospective analysis of 2 AMS (Voluntary Milking System, DeLaval, Tumba, Sweden) was performed on data collected from 2004 to 2006 and 2012 to 2018 at the Danish Cattle Research Center (Foulum, Denmark). Hourly AMS visits were analyzed using an ANOVA (GLIMMIX Procedure, SAS 9.4, Cary, NC, USA). Fixed effects included days in milk (DIM), parity (primiparous and multiparous), occupation rate, h, and interaction of occupation rate and h, with yr and AMS by yr considered random effects. FPCM was assessed by linear mixed models using the MIXED procedure. Fixed effects of parity and week in milk were included in all models. We also tested the polynomial effects of stocking density at a quartic relationship. Random effects were defined as AMS, week, and week nested within year. Fixed effects remained in the model regardless of significance. Stocking density averaged 56.3 ± 4.3 and 55.9 ± 4.6 cows per AMS (range: 38 to 64). Parity, DIM, occupation rate, h, and occupation rate by h were associated with hourly AMS visits (F ≥44.7, P < 0.001, DF = 141862). As occupation rate increased, cows were most likely to visit the AMS at 8:00, 16:00, and 17:00. Hourly AMS use was lowest from 2:00 to 4:00 and was unrelated to occupation rate (t <1.14, P ≥ 0.22). Mean FPCM per AMS was greater at 60 to 64 cows per AMS (2356.9 ± 82.0 kg) compared with <60 cows (2002.4 ± 97.9 kg; t ≥11.9; P < 0.001), suggesting that FPCM per AMS had plateaued. Stocking density affected hourly occupation rate and FPCM. Results from this study suggest a stocking density of 60 to 64 cows within an AMS, while considering optimal cleaning times, is key for maximizing productivity.