This article compiles and quantitatively describes the results of over 25,000 social psychological studies involving 8 million participants. It aims to summarize the best-established findings in social psychology, providing a comprehensive overview of the field's research over the past century. The authors use meta-analysis to quantify the magnitude and variability of social psychological effects, revealing that typical effects yield a correlation coefficient of r = .21, with a standard deviation of r = .15 across studies. The article also discusses the limitations and implications of this large-scale compilation, highlighting the importance of understanding the size and consistency of social psychological effects for research planning and statistical power computation. Additionally, it addresses the variability of effects, noting that much of the variation is due to sampling error and the manipulability of effects by researchers. The study concludes by emphasizing the need for cautious interpretation of meta-analytic means, especially in contexts where effects are manipulated or reversed.This article compiles and quantitatively describes the results of over 25,000 social psychological studies involving 8 million participants. It aims to summarize the best-established findings in social psychology, providing a comprehensive overview of the field's research over the past century. The authors use meta-analysis to quantify the magnitude and variability of social psychological effects, revealing that typical effects yield a correlation coefficient of r = .21, with a standard deviation of r = .15 across studies. The article also discusses the limitations and implications of this large-scale compilation, highlighting the importance of understanding the size and consistency of social psychological effects for research planning and statistical power computation. Additionally, it addresses the variability of effects, noting that much of the variation is due to sampling error and the manipulability of effects by researchers. The study concludes by emphasizing the need for cautious interpretation of meta-analytic means, especially in contexts where effects are manipulated or reversed.