How long does 250 mg of caffeine last?
About 15 and a half hours. 250 mg of caffeine peaks near 228 mg 45 minutes after you take it, halves every 5.7 hours, and falls below the 40 mg sleep threshold about 15 and a half hours later.
| Peak level, 45 minutes in | 228 mg |
| Time to fall below 40 mg | 15 and a half hours |
| Left after 6 hours | 123 mg |
| Left after 12 hours | 60 mg |
| Latest hour for an 11 pm bedtime | 7:44 am |
| Share of the 400 mg daily limit | 62% |
Hour by hour
| Time after the dose | If taken at 8 am | Still active | For sleep |
|---|---|---|---|
| 1 hour | 9 am | 225 mg | still working |
| 2 hours | 10 am | 201 mg | still working |
| 4 hours | 12 pm | 157 mg | still working |
| 6 hours | 2 pm | 123 mg | still working |
| 8 hours | 4 pm | 97 mg | still working |
| 10 hours | 6 pm | 76 mg | still working |
| 12 hours | 8 pm | 60 mg | still working |
| 16 hours | 12 am | 37 mg | clear |
| 24 hours | 8 am | 14 mg | clear |
What 250 mg looks like
250 mg is a large cold brew, a can and a half of Monster, or a coffee on top of an energy drink. It is above the 200 mg that the European Food Safety Authority treats as a safe single dose, though still well inside the 400 mg daily limit.
Taken at once it peaks near 228 mg, a level at which people who are not used to caffeine often report jitters and a fast pulse. Spread over a morning the same amount is unremarkable. What changes little is the clock: either way the last of it needs most of the day to leave.
| Drink | One serving | To reach 250 mg |
|---|---|---|
| Filter coffee | 96 mg per 8 oz cup | 2.6 |
| Espresso | 64 mg per 1 oz shot | 3.9 |
| Black tea | 48 mg per 8 oz cup | 5.2 |
| Red Bull | 80 mg per 8.4 oz can | 3.1 |
| Coca-Cola | 32 mg per 11.2 oz can | 7.8 |
How late can you take it?
Count back 15 and a half hours from the time you go to bed. Each bedtime below has its own page with the cutoff for every drink.
| Bedtime | Latest hour for 250 mg |
|---|---|
| 9 pm | 5:44 am |
| 9:30 pm | 6:14 am |
| 10 pm | 6:44 am |
| 10:30 pm | 7:14 am |
| 11 pm | 7:44 am |
| 11:30 pm | 8:14 am |
| midnight | 8:44 am |
| 1 am | 9:44 am |
If you clear caffeine faster or slower
Half-life runs from about four hours in fast metabolisers to eight or more in slow ones, and the difference compounds over a day.
| Metabolism | Half-life | Clears in | Latest for 11 pm |
|---|---|---|---|
| Fast | 4.1 hours | 11 hours | 11:56 am |
| Average | 5.7 hours | 15 and a half hours | 7:44 am |
| Slow | 7.9 hours | 21 hours | 2:01 am the night before |
Common questions
How long does 250 mg of caffeine last?
About 15 and a half hours for an average adult. 250 mg peaks near 228 mg active 45 minutes after you take it, then halves every 5.7 hours until it falls below 40 mg, the line Cira uses as low enough to sleep on.
Is 250 mg of caffeine a lot?
As a single dose, yes. 250 mg is above the 200 mg that the European Food Safety Authority considers safe to take at once. As a day's total it is within the 400 mg limit for a healthy adult.
How late can I take 250 mg of caffeine and still sleep?
For an 11 pm bedtime the latest is 7:44 am. Move it by the same amount as your own bedtime. People who clear caffeine slowly need about 21 hours, so they should stop earlier still.
How much of a 250 mg dose is left after 12 hours?
About 60 mg, for an average adult. After 6 hours about 123 mg is still active, and after 24 hours about 14 mg.
Other doses
Look it up another way
Where these numbers come from
Every figure is calculated with the model the Cira app uses: caffeine peaks 45 minutes after you take it and halves every 5.7 hours, a typical value for healthy adults. The 40 mg sleep line is a working threshold of the model, and the 400 mg daily limit is the figure used by the European Food Safety Authority and the US FDA. These are averages. Smoking, pregnancy, the contraceptive pill and some medicines change how fast you clear caffeine. How the numbers are worked out.
