Evidence and editorial policy
Sources and editorial policy
Where do our figures come from? We look for the brand’s own product information, published research and government guidance. You’ll find the links here and beside the relevant figures, so you can check them yourself.
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.
Gardiner et al. (2023): The Effect of Caffeine on Subsequent Sleep
A systematic review and meta-analysis examining how caffeine dose and timing affect subsequent sleep.
Clark and Landolt (2017): Coffee, Caffeine, and Sleep
A systematic review of epidemiological studies and randomised controlled trials.
Late-Afternoon and Evening Pre-Exercise Caffeine and Sleep (2025)
A systematic review and meta-analysis focused on caffeine before later training or competition.
Wikoff et al. (2017): The Safety of Ingested Caffeine
A comprehensive peer-reviewed review of caffeine safety and metabolism.
How drink data is recorded
Each drink has a country, serving size, source link and date checked. We use the brand’s current figures where we can. If an amount is older, approximate or comes from another source, we add a clear warning beside it rather than making it look equally certain.
We don’t convert a published range into a midpoint, infer caffeine from calories or transfer a formulation from another market. Browse the UK caffeine database, download its CSV data or inspect the machine-readable JSON.
How guides are produced
We start with a question you might actually have about your coffee, tea or caffeine habits. Calculation examples use the same formula as the tools and are labelled as estimates. Articles link to the research behind the discussion. We use AI to help with drafting, but don’t claim that the guides have had an independent medical review.
Updates and corrections
Published and updated dates change only when the main content, calculations, sources or links change materially. Product caffeine values are taken from current manufacturer or public data where possible, but formulations vary by serving and market. Readers can report corrections through the contact link on the About page.
Independence and limitations
CaffCalc is maintained by an independent developer, not a medical practice. It doesn’t sell supplements or accept payment for caffeine values. Some pages contain clearly labelled affiliate links, which don’t influence the calculator’s formula, drink data or editorial conclusions.