When should you stop drinking coffee before bed?

It’s the question every coffee lover eventually asks: how late is too late for a coffee? The honest answer is that there’s no single number that works for everyone — but there is a way to think about it clearly.

Why there’s no universal rule

Caffeine doesn’t leave everyone’s body at the same speed. How quickly you clear it depends on your genetics, your liver, whether you smoke, some medications, and hormonal factors such as pregnancy or oral contraception. Two people can drink the same espresso at 4 p.m. and have very different amounts left at midnight.

That’s why a fixed “stop at 2 p.m.” rule is, at best, a rough average — and at worst, wrong for you specifically.

What the science says about timing

Caffeine has a long half-life — commonly cited around five to six hours, though it varies a lot between individuals. A half-life of five hours means that five hours after your cup, roughly half of the caffeine is still circulating.

In a frequently cited study, researchers found that 400 mg of caffeine taken even six hours before bed measurably reduced sleep (Drake et al., 2013). The takeaway isn’t “never drink coffee” — it’s that an afternoon cup can still be active when your head hits the pillow.

A practical way to find your cutoff

Rather than guessing, work backwards from your bedtime:

1. Note when you want to fall asleep.
2. Account for caffeine’s long tail — for many people, that means keeping larger doses out of the late afternoon and evening.
3. Pay attention to how you actually sleep, and adjust.

If a great cup would push past your line, a quality specialty decaf keeps the ritual without the caffeine.

Let your body do the math

Tracking this by hand is tedious. CaffIQ estimates your live caffeine level and calculates a personal cutoff time from your own profile — so you can see, in real time, how late you can still enjoy a coffee tonight.

CaffIQ provides general estimates, not medical advice. For any health question, consult a qualified professional.