A calmer way to understand caffeine

What this site is

You tell the calculator what you drank, when you drank it, and a few details about your metabolism. It estimates how much caffeine is still in your body now and later in the day, including around your bedtime.

How the estimate works

Each drink is treated as clearing at a steady rate set by a half-life, and all drinks are added together. The full formula is explained on the home page.

Our principles

• Private by design. The calculation runs in your browser. Nothing you enter is sent to us.
• Honest about limits. Results are estimates. People differ, and no amount is right or wrong for everyone.
• Free and simple. No accounts, no sign-up, and no ads in the calculator.

Learn more about caffeine

Want the background behind the numbers? Read how long caffeine lasts, the half-life of caffeine, what changes how fast you clear caffeine, or how much caffeine is in common drinks.

Not medical advice

CaffeineLeft is for general information only. If you are pregnant, take medication or have a health condition, speak with a doctor or pharmacist. Questions or feedback? Get in touch.