Last updated: September 24, 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 model defaults to a five-hour caffeine half-life for an average adult, and you can switch between fast (four hours), average (five), and slow (seven) presets. 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.
Who maintains CaffCutoff
CaffCutoff is written and maintained by cisyWang. The site focuses on caffeine timing rather than daily intake limits, because the practical question for most people is when a drink stops mattering, not whether it counts. Every guide states the assumption it is built on, so you can judge how much weight to give the estimate.
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.
Embed the calculator on your own site
Coffee blogs, fitness sites, and workplace wellbeing pages are welcome to embed the compact bedtime calculator. It loads in an isolated frame, sets no cookies, stores nothing, and needs no account or API key. Paste this snippet wherever you want it to appear:
<iframe
src="https://caffcutoff.com/embed/"
title="Caffeine left at bedtime calculator"
width="100%"
height="430"
style="border:0;max-width:560px"
loading="lazy"
></iframe>The widget links back to the full CaffCutoff calculator, which adds multiple drinks, a cutoff time, and a decay timeline.
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.