Half-life isn’t half-truth
Caffeine’s half-life ranges from ~3 to 10 hours depending on genetics, liver enzymes, and even pregnancy. Night owls can’t always blame espresso—sometimes it’s DNA.
Metabolism quirks
☕😴 Coffee-to-Sleep Tradeoff
Your Inputs
Typical: espresso ~60–75 mg, brewed coffee ~80–150 mg, tea ~20–60 mg.
Local time today.
~5.0 h (adjust if you metabolize faster/slower)
How strongly caffeine affects your sleep.
You can add several cups; we’ll combine them.
Kind rule: information, not judgment.
Results
Residual caffeine at bedtime –
Estimated bedtime delay –
Estimated sleep affected –
Assumes simple half-life decay and your selected sensitivity. Not medical advice.
Tip: If delay feels high, try moving the last caffeinated drink earlier, choosing a smaller dose, or switching to decaf after lunch.
How the calculator estimates sleep impact (friendly science)
Caffeine doesn’t turn off instantly—it fades gradually. A common way to describe that fade is a half-life: the time it takes for the active amount to drop by half. For many adults, a reasonable default is around five hours, though three to seven hours is still common depending on genetics, liver enzyme activity, medications, and timing. This tool lets you adjust the half-life so the results feel closer to your experience.
The math is gentle. For each drink, we estimate the fraction remaining at bedtime using simple exponential
decay: remaining = dose × 0.5^(hours_until_bed / half_life). If you add multiple drinks, we sum the
remaining amounts. That total becomes your residual caffeine at bedtime. From there, we translate the
residual into a bedtime delay and a rough sleep-lost estimate using a smooth curve that scales
with sensitivity. Think of it as a friendly yardstick: more residual caffeine tends to push bedtime later and
can reduce total sleep time, especially if your schedule is fixed.
Sensitivity matters a lot. Some people can sip an evening espresso and drift off. Others feel wired after a small tea. That’s why we include three presets—Low, Typical, and High—that change how strongly a given residual amount translates to delay and sleep loss. No judgment, just sliders. If your real-world experience differs (e.g., you’re unusually sensitive or very tolerant), set the sensitivity to match your reality and treat the numbers as guidance, not rules.
Finally, a kindness note: your sleep is influenced by many things—light exposure, stress, meals, exercise, temperature, and more. This calculator focuses only on caffeine timing and dose to offer a quick, private “what if?” view. Use it to nudge choices (earlier last cup, smaller dose, or decaf after lunch) and to build your own intuition. It’s not medical advice, and it doesn’t diagnose or treat sleep disorders. If you have concerns about sleep, consider speaking with a qualified professional.
Privacy & accessibility: everything runs locally in your browser; inputs aren’t uploaded. Results are announced via ARIA live regions for assistive tech.
5 Fun Facts about Caffeine & Sleep
Adrenaline sneak attack
Caffeine doesn’t just block adenosine; it also nudges adrenaline. That’s why a late latte can feel like a mini stress burst right when you’re trying to unwind.
Hidden buzz
Naps love caffeine (in micro doses)
A “coffee nap” works because caffeine takes ~20 minutes to kick in. Sip, nap, wake as it peaks—alertness spikes higher than either alone for many people.
Hacky combo
Afternoon light helps detox
Bright daylight boosts adenosine buildup, counteracting caffeine’s blockade. A brisk daylight walk after lunch can shrink the bedtime delay from an early-afternoon coffee.
Light assist
Decaf isn’t zero
Decaf still carries 2–5 mg per cup. That’s tiny, but if you sip several mugs late and are ultra-sensitive, it can still register.
Tiny dose