We estimate the global impact of COVID-19 on student reading using international achievement tests. We model the effect of school closures (full and partial) on achievement by predicting the deviation of the most recent results from a linear trend using data from all rounds of PIRLS. Scores declined an average of 33 percent of a standard deviation, equivalent to more than a year of schooling. Losses are larger for students in schools that faced relatively longer closures. While there are no differences by sex, lower-achieving students experienced larger losses. The educational loss may translate to a 0.68 percentage point reduction of GDP growth for a global loss of $66 trillion.