Caffeine Calculator
When you need to check caffeine, the Caffeine gives you a clear starting point. Enter one realistic example first, then compare another option if useful.
Caffeine remaining
—
Of daily limit—
Half-life is about 5 to 6 hours; 400 mg/day is a common adult limit. This is an estimate for general guidance, not medical advice. For a plan that fits you, talk to a doctor or qualified professional.
✉ Email me this result
</> Embed this calculator
Paste this into any website or blog post. It is free — the small "powered by" link must stay visible.
How it works
Remaining = intake × 0.5^(hours ÷ 5.7)How to use the Caffeine
Enter the requested values and start with one realistic example. Read the result together with its unit or label, then change one input at a time if you want to compare options.
This is a general estimate and cannot replace advice from a qualified health professional.
Frequently Asked Questions
How does the Caffeine Calculator work?
See how much caffeine is left in your system after a number of hours.
Is this medical advice?
No. It gives general estimates only. For decisions about your health, speak with a qualified professional.
Can I use the result as an exact answer?
Treat it as an estimate or check unless the page and the rules that apply to you confirm otherwise. Rounding, fees and personal details can change the final result.