All data is embedded directly in the calculator as JavaScript constants. No external API calls are made. You can verify the accuracy of any figure by comparing it to the primary sources linked below.
Developmental Milestone Data
CDC
CDC Learn the Signs. Act Early. — Developmental Milestones (2022 Revision)
Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities. Learn the Signs. Act Early. Developmental Milestones. Revised 2022. This is the primary source for all developmental milestone checklists displayed in the Parent Mode section of AgeInMonths.com. The 2022 revision updated milestone language and some age assignments based on the latest developmental research. Milestones are provided for ages 2, 4, 6, 9, 12, 15, 18, 24, 30, 36, 48, and 60 months across four developmental domains: social and emotional, language and communication, cognitive, and movement and physical development.
CDC
Zubler JM, et al. — Evidence-Informed Milestones for Developmental Surveillance Tools (2022)
Zubler JM, Wiggins LD, Macias MM, et al. Evidence-Informed Milestones for Developmental Surveillance Tools. Pediatrics. 2022;149(3):e2021052138. This peer-reviewed paper provides the evidence base for the 2022 CDC milestone revisions. The paper reviewed over 2,500 published studies to establish milestone timing at the 75th percentile of children — meaning 75% of children are expected to reach each milestone by the listed age.
Life Expectancy Data
CDC
CDC National Vital Statistics Reports — United States Life Tables (Most Recent Edition)
Arias E, Xu JQ. United States Life Tables. National Vital Statistics Reports. Centers for Disease Control and Prevention, National Center for Health Statistics. This report provides complete period life tables for the US population by age, sex, and race/Hispanic origin. The life expectancy at birth and remaining life expectancy values by age embedded in this calculator are taken from the most recent edition's all-cause, all-race combined tables.
Supporting Data
BLS
Bureau of Labor Statistics — American Time Use Survey
US Bureau of Labor Statistics. American Time Use Survey Summary. Annual release. The figure of approximately 1.5 hours per day spent eating and drinking used in the "time spent eating" calculation is derived from the BLS American Time Use Survey, which measures how Americans spend their time across all activities.
General
Resting heart rate — 70 beats per minute
The resting heart rate of 70 beats per minute used in the heartbeat calculation is a standard population average figure cited by the American Heart Association and in medical reference literature. Normal adult resting heart rate ranges from 60 to 100 beats per minute. 70 bpm is commonly used as the reference value for population-level calculations.
Want to verify the data?
All data embedded in AgeInMonths.com is publicly available from the primary sources linked above. If you find a discrepancy between our embedded data and the current CDC or BLS publications, please let us know. Data accuracy — especially for the developmental milestone content — is important to us.