See when your caffeine will wear off and when you should stop drinking coffee to sleep well.
Caffeine has an average half-life of about 5 hours in most adults, meaning half of the caffeine is still in your system 5 hours after consumption. After 10 hours, about 25% remains. Individual half-life can range from 3-7 hours depending on genetics, age, liver function, pregnancy, and medications. Smoking shortens it; oral contraceptives lengthen it.
The FDA considers 400mg of caffeine per day safe for most healthy adults. That's roughly 4 cups of drip coffee. For good sleep, most sleep researchers recommend having less than 25-50mg of caffeine in your system at bedtime. This calculator uses the 5-hour half-life to estimate your caffeine level at bedtime.