Your cortisol peaks. Your chronotype shifts it. Your medication changes everything. This calculator gives you a science-backed daily caffeine schedule — personalised to your biology.

When do you sleep?

We'll anchor everything to your natural rhythm.

Wake up time Bedtime

Your caffeine year

optimal cups / year

cups avoided too early

nights saved from late coffee

Cortisol peak clearance

Cortisol spikes 30–45 min after waking and peaks around 8–9am for most people. Drinking coffee during this window reduces caffeine's effectiveness because the two alertness mechanisms compete. Waiting 90 min allows cortisol to fall, giving caffeine full impact. Source: Lovallo et al. (1996)

first coffee window

first_coffee = wake + 90 min + chronotype_offset ADHD modifier: −30 min (blunted cortisol peak)

Chronotype shift

Chronotype is a genetic trait that shifts the entire circadian rhythm. Night Owls have a phase-delayed cortisol curve — their peak comes later, so their first safe coffee window is also later. Early Birds are the reverse. Source: Roenneberg et al. (2007)

chronotype offsets

Early Bird: −30 min · Intermediate: 0 min Night Owl: +75 min · ADHD: additional −30 min

Caffeine half-life and cutoff

Caffeine has a half-life of 5–6 hours. For full clearance (under 50mg active), you need 8–10 hours before sleep, adjusted for individual sensitivity. The cutoff calculation ensures caffeine doesn't interfere with sleep quality even if you can fall asleep with caffeine in your system. Source: Drake et al. (2013)

cutoff calculation

cutoff = bedtime − sensitivity_hours Low: −6h · Medium: −8h · High: −10h ADHD: additional −1h (sleep latency)

ADHD and medication interactions

ADHD involves blunted cortisol amplitude and a delayed circadian phase independent of chronotype. Stimulant medications create a peak-and-trough cycle that strongly interacts with caffeine — combining them at peak plasma concentration significantly increases cardiovascular stress and anxiety. The medication separation windows are based on published pharmacokinetic data for each drug class.

stimulant separation windows

Ritalin IR: coffee OK until 20 min before, or 3h+ after Concerta XR: coffee OK until 20 min before, or 5h+ after Adderall IR: coffee OK until 20 min before, or 4h+ after Vyvanse: coffee OK until 20 min before, or 7h+ after

☕ optimise further

Your brain runs on timing.

Small shifts in when you drink coffee compound over months. Here's what the science says makes the biggest difference.

🌅

Delay your first cupEven 30 minutes past cortisol peak measurably improves afternoon energy. The initial grogginess is cortisol doing its job — let it.

💧

Hydrate before caffeinatingCaffeine on an empty, dehydrated stomach raises cortisol and blunts the effect. 250ml water first changes how the first cup feels.

⏱️

Respect the cutoff seriouslyCaffeine at 50% of half-life still disrupts deep sleep architecture — even if you fall asleep fine. Sleep quality, not just duration, matters.

free resource

Huberman Lab — Morning Routine

Cortisol + caffeine protocols

recommended book

Why We Sleep — Walker

How caffeine truly disrupts sleep

app · iOS

RISE — Sleep & Energy Tracker

Tracks your circadian rhythm daily

reference

Sleep Foundation — Caffeine

Research overview, accessible

Methodology note: Caffeine timing recommendations are based on peer-reviewed chronobiology and pharmacokinetics research. ADHD and medication interaction data reflects published pharmacokinetic profiles and is a general reference tool, not medical advice. Medication timing windows are conservative estimates — consult your prescribing doctor before changing your routine. Sources: Lovallo et al. (1996) · Drake et al. (2013) · Roenneberg et al. (2007). Not a substitute for medical advice.

Your Coffee Time.