Last updated: August 18, 2026
A clearer answer to the last-cup question
CaffCutoff is a free browser-based tool for people who want a practical estimate of how today's caffeine may carry into bedtime. Add each drink, choose a target bedtime, and the calculator estimates the remaining caffeine, an input-based cutoff for another drink, and a decay timeline.
What the calculator provides
- An estimated caffeine amount remaining at bedtime.
- An input-based cutoff estimate for a selected next dose.
- An estimate of when caffeine may fall below 5 mg.
- A timeline built from multiple drinks and intake times.
- A lightweight caffeine persona designed for sharing, not diagnosis.
How the estimate works
The current model uses a five-hour caffeine half-life for an average adult. Each recorded dose decays independently, and the estimated remainders are added together. The 25 mg bedtime value is a planning target used by this tool, not a medically established safety threshold.
Privacy by design
CaffCutoff does not require an account, backend, or database. Calculator inputs are processed in your browser. This keeps the product fast and limits the personal information needed to use it.
What CaffCutoff cannot tell you
A formula cannot measure your personal metabolism or predict sleep quality. Genetics, pregnancy, smoking, medications, health conditions, and individual sensitivity can materially change caffeine clearance. Use the result as a planning aid and pay attention to your own response.