Sleep & Caffeine Timeline

Every caffeinated drink you consume adds to the caffeine already in your system. Because caffeine has a half-life of 4-6 hours, a morning coffee hasn't fully cleared by the time you have an afternoon drink. The two amounts stack together, which is why your total caffeine level can climb higher than any single drink would suggest. This tool calculates the combined curve so you can see exactly how much caffeine is in your body at any point.

Caffeine stacking is when residual caffeine from an earlier drink is still active in your body when you consume another. For example, if you drink a coffee at 8 AM and another at noon, roughly half of the first coffee's caffeine is still present when you add the second. The combined level may push your total well above the amount from a single cup, which can delay your sleep-ready time significantly.

Sleep researchers generally recommend having less than 50 mg of caffeine in your system at bedtime, and ideally under 25 mg. Above 100 mg, most people experience noticeable difficulty falling asleep, lighter sleep stages, and less restorative deep sleep. The exact threshold varies by individual, but keeping your bedtime level below 50 mg is a good starting guideline.

Absolutely. The same amount of caffeine will have very different effects on your sleep depending on when you drink it. A coffee at 7 AM has around 13-14 hours to decay before a 10 PM bedtime, leaving very little in your system. The same coffee at 3 PM only has 7 hours, leaving a substantial amount. Use this timeline tool to experiment with different timing and see the impact.

A common rule of thumb is 8-10 hours before bedtime, but this depends on the amount you drink and your metabolism speed. Someone with fast caffeine metabolism (4-hour half-life) might be fine with a small tea 6 hours before bed, while a slow metabolizer (6-hour half-life) might need 12+ hours. This tool lets you model your specific situation rather than relying on general advice.