Caffeine Calculator
How long does caffeine stay in your system? Enter your intake below and see a visual timeline based on caffeine's 5.5-hour half-life.
How it works:Caffeine has an average half-life of 5.5 hours — meaning half the caffeine is still in your body after 5.5 hours. Select your drink or enter a custom amount to see when you'll be caffeine-free.
About caffeine half-life
Caffeine is the world's most widely consumed stimulant. It's absorbed within 45 minutes of consumption and reaches peak blood levels at 30-60 minutes. The average half-life is 5-6 hours, but this varies significantly between individuals.
For optimal sleep, experts recommend keeping caffeine below 50mg in your system at bedtime. This calculator helps you find the right cutoff time based on your actual intake.
Frequently asked questions
How long does matcha caffeine last?
Matcha contains ~70mg of caffeine per cup — similar half-life to coffee (5.5 hours). However, matcha also contains L-theanine, which creates a smoother, more sustained energy without the jitters.
How much caffeine is safe per day?
The FDA considers 400mg per day (about 4 cups of coffee) safe for most healthy adults. Pregnant women should limit to 200mg. Individual tolerance varies.
Does caffeine affect everyone the same way?
No. Genetics play a major role — some people metabolize caffeine quickly (half-life ~3 hours) while others are slow metabolizers (half-life ~9 hours). Age, medications, and liver health also affect caffeine metabolism.