The Partition of India in 1947 along ostensibly religious lines into India, Pakistan, and what eventually became Bangladesh resulted in one of the largest and most rapid migrations in human history. In this paper district level census data from archives are compiled to quantify the scale of migratory flows across the subcontinent.We estimate total migrator y inf lows of 14.5 million and outflows of 17.9 million, implying 3.4 million “missing” people. The paper also uncovers a substantial degree of regional variability. Flows were much larger along the western border, higher in cities and areas close to the border, and dependent heavily on the size of the “minority” religious group. The migratory flows also display a “relative replacement effect” with in-migrants moving to places that saw greater outmigration.