How Many Hours Before Bed Should I Stop Caffeine?

For an average-sized coffee, stop caffeine about 8–10 hours before bed. That window lets a roughly 95 mg dose fall below the ~50 mg level where caffeine starts to disrupt sleep. But the "8–10 hour rule" is a starting point, not a law — your real cutoff shifts earlier with bigger drinks and slower metabolism, and later if you're a small-cup, fast-clearing drinker. Here's how to find your number.

Where the "8–10 hours" rule comes from

Caffeine leaves your body on a predictable curve. Its half-life averages about 5 hours, so every 5 hours the amount in your system roughly halves. Start with a 95 mg cup and you're at ~48 mg after 5 hours, ~24 mg after 10 hours.

Sleep researchers find most people sleep best with less than about 50 mg of caffeine on board at bedtime — a 2025 meta-analysis of controlled crossover trials found caffeine cut total sleep time and slow-wave sleep in a dose-dependent way. Do the math on an average coffee and an average metabolism, and 8–10 hours is the span it takes to drop under that line. That's the whole basis of the rule — one assumed dose, one assumed metabolism.

The problem: almost nobody is exactly average on both.

Why it's a starting point, not a law

Two facts blow up the one-size-fits-all version:

• Half-life ranges from about 3 to 9 hours between people — a fast metabolizer clears caffeine nearly three times quicker than a slow one (what determines your side).
• Dose scales the clearance time. Each doubling of the dose adds roughly one half-life — about 5 more hours — before you fall below 50 mg.

A landmark controlled study by Drake and colleagues (2013) gives the rule its teeth: a 400 mg dose taken even 6 hours before bed cut objectively measured sleep by more than an hour — and participants often didn't notice. That's why "just don't drink it right before bed" isn't enough. The damage happens hours upstream.

How many hours you actually need, by dose

Using a 5-hour half-life (an average metabolizer), here's how long it takes a single drink to fall under the ~50 mg sleep threshold:

These assume average clearance. A slow metabolizer should add several hours to every row; a fast metabolizer can shave a few off. (That bottom row also sits at the FDA's 400 mg daily ceiling for healthy adults — a reason to keep it a morning-only dose.)

👉 These are averages. To see exactly how many hours you need for your drink, your dose and your bedtime, try the calculator.

How to personalize your cutoff in three steps

1. Anchor to your bedtime, not the clock

"Stop at 2 PM" is meaningless if you don't know when you sleep. Count backward from your target bedtime instead. If you're in bed at 11 PM and need a 9-hour buffer, your last call is 2 PM. Our coffee cutoff time by bedtime guide maps this out for every bedtime.

2. Adjust for your dose

A double espresso isn't a single cup. Size up the drink, size up the buffer — add roughly 5 hours per doubling of caffeine. The table above is your cheat sheet.

3. Adjust for your metabolism

This is the biggest lever. If coffee "hits you hard," lingers into the evening, or wrecks your sleep even from an early cup, you're likely a slow metabolizer and should push your cutoff earlier. If you can drink it at 5 PM and sleep fine, you're probably fast. Find your type with Are you a fast or slow caffeine metabolizer?.

The bottom line

The 8–10 hour rule is a useful default, but it's built on an average drink and an average body. Bigger doses need an earlier cutoff; slower metabolism needs an earlier cutoff; the threshold that actually matters is ~50 mg at bedtime. Don't memorize a number off the internet — calculate it from your own drinks, your own bedtime, and your own clearance rate.

Stop guessing your cutoff. The Caffeine & Sleep app logs every drink in one tap, models your personal caffeine curve from your dose and metabolism, and pings you 30 minutes before your real last-call time — so you always know exactly how many hours before bed to stop. Get the app →