Caffeine Calculator
How much caffeine is still in your body at bedtime.
These are estimates based on standard formulas, not medical advice.
Runs entirely in your browser. Nothing is sent anywhere.
How it works
- 1Enter your values.
- 2See the result update instantly as you type.
- 3Change any value to compare scenarios.
About this tool
Caffeine Calculator: How much caffeine is still in your body at bedtime. Type your numbers and the result is calculated instantly — no button to press, nothing to install. All math runs locally in your browser, so the values you enter are never sent anywhere.
Example
| Input | |
|---|---|
| Bedtime | 23:00 |
| Half-life (hours) | 5 |
| Result | |
| Caffeine at bedtime | 66 mg |
| Total consumed | 253 mg |
| Below 50 mg from | 01:05 |
How do I use the Caffeine Calculator?
Enter your values. See the result update instantly as you type. Change any value to compare scenarios.
Is the Caffeine Calculator free?
Yes. It is completely free with no sign-up, no usage limits and no watermark.
Is my data sent to a server?
No. Everything is calculated locally in your browser. Nothing you enter is uploaded, logged or stored.
Does it work on my phone?
Yes. It works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux — no app needed.