How much caffeine is too much?

The FDA considers 400mg/day safe for healthy adults. Single doses above 200mg can cause anxiety, jitteriness, or elevated heart rate in sensitive individuals.

When should I stop drinking coffee for a good night's sleep?

With a 5.5-hour half-life, a 200mg coffee at 2pm leaves ~50mg by 10pm. For sensitive sleepers, stop caffeine at least 8–10 hours before bedtime.

Caffeine Half-Life Calculator

Caffeine has a half-life of approximately 5–6 hours in most adults — meaning half of it is eliminated every 5–6 hours. If you drink a 200mg coffee at noon, you'll still have ~100mg in your system at 6 PM and ~50mg at midnight. Use this calculator to find the optimal cut-off time for your last coffee of the day.

Caffeine Consumed (mg)

Hours Since Consumed

Your Half-Life

How to Use This Calculator

1
Enter the total caffeine consumed (see FAQ for common amounts).
2
Enter how many hours ago you consumed it.
3
Select the half-life that best matches your profile.
4
Click Calculate to see how much caffeine is still in your system.

Frequently Asked Questions

Espresso shot: ~63mg. Regular brewed coffee (8oz): ~95mg. Double espresso latte: ~126mg. Red Bull (8.4oz): 80mg. Tea (8oz): 47mg. Cola (12oz): 34mg.

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