This report provides methodological details on the estimates presented in Adding It Up: Investing in Sexual and Reproductive Health 2019. Adding It Up is a recurring Guttmacher Institute study in which researchers estimate the need for, impact of and cost of fully investing in sexual and reproductive health care. Estimates for 2019 focus on contraceptive services, maternal and newborn care, abortion services and treatment for the major curable STIs for women of reproductive age (15­–49) in 132 low- and middle-income countries. In this methodology report, we describe the study’s analytical framework and data sources, assumptions used to calculate the estimates and limitations of the estimates.