Caffeine Curfew Calculator: When to Stop Coffee Before Bed

Sleep & caffeine planner

Caffeine Curfew Calculator

Estimate when to stop caffeine before bed using a chosen caffeine half-life, your last dose and your target bedtime. It is a planning tool—not proof that caffeine will be fully cleared or that your sleep will be unaffected.

Calculate your caffeine curfew

Target bedtime

Time of your most recent caffeine

Estimated caffeine in that drink (mg)

Check the label where possible. Drink sizes and recipes vary considerably.

Planning half-life3 hours — faster clearance estimate5 hours — common planning midpoint7 hours — cautious estimate9 hours — very cautious estimate

Caffeine clearance varies between people and circumstances; this menu makes that uncertainty visible.

Enter your details, then select Calculate curfew.

Quick caffeine guide

Use product labels rather than this table for a precise figure.

Common serving	Often roughly
Instant coffee	50–90 mg
Espresso	60–80 mg
Black tea	30–50 mg
Energy drink (250 ml)	About 80 mg

Decaf products can still contain a small amount of caffeine.

Why a curfew instead of “full clearance”? Caffeine declines gradually: after one half-life, roughly half remains; after three, around 12.5% remains. This page uses three half-lives before bed as a conservative, simple target—not a medical rule. A study found sleep disruption when caffeine was taken six hours before bedtime, so people sensitive to caffeine may benefit from an earlier curfew.

How the caffeine calculator works

The calculator uses the standard exponential-decay model: remaining caffeine = starting dose × 0.5^{(hours elapsed ÷ half-life)}. It displays an estimate of the caffeine from the most recent drink still present at bedtime, plus a suggested last-caffeine time based on the half-life you selected.

A half-life is not a personal diagnosis. Caffeine processing can be affected by pregnancy, some medicines, liver disease, smoking status, age and genetic differences. Coffee also is not the only source: tea, energy drinks, cola, chocolate, pre-workout products and some cold-and-flu remedies may contribute.

If sleep is the priority, try the cautious setting for a week while keeping bedtime and wake-up time reasonably stable. A printable caffeine log can help identify patterns better than a one-off calculation: note the drink, estimated dose, time, sleep onset and how rested you feel the next day.

Caffeine curfew FAQs

What is the best time to stop drinking coffee before bed?

There is no universal cut-off. Six hours is a useful minimum starting point for many people, but a longer window may suit anyone who is caffeine-sensitive or regularly struggles to fall asleep.

Does a coffee at 3 pm affect sleep at 11 pm?

It can. With a five-hour half-life, an estimated 100 mg dose at 3 pm would leave roughly one-third of that amount by 11 pm. The practical effect varies by dose and individual sensitivity.

Should I use this calculator during pregnancy?

Use it only as general information. Caffeine advice in pregnancy is more cautious; discuss your intake with a midwife, GP or pharmacist and check current NHS guidance.

What if I cannot sleep despite avoiding caffeine?

Persistent insomnia, loud snoring or marked daytime sleepiness deserves clinical advice. Caffeine may be one factor among many, including stress, shift work, pain, medicines and sleep disorders.

Sources: caffeine half-life variability is described by the NCBI pharmacology reference; sleep effects up to six hours before bed were reported by Drake et al. This page is for education and is not medical advice.