Evidence and editorial policy
Sources
We prefer primary research, government guidance and manufacturer data. Sources are linked so readers can inspect the evidence themselves.
FDA: Spilling the Beans — How Much Caffeine Is Too Much?
Consumer guidance and the often-cited 400 mg daily level for most healthy adults.
Drake et al. (2013): Caffeine Effects on Sleep
A controlled study of 400 mg caffeine taken 0, 3 or 6 hours before bedtime.
Wikoff et al. (2017): The Safety of Ingested Caffeine
A comprehensive peer-reviewed review of caffeine safety and metabolism.
Editorial approach
Calculator assumptions are separated from medical claims. Material changes to sources or calculations should be reviewed and dated. CaffCalc does not sell supplements and accepts no payment for caffeine values.