How long does 50 mg of caffeine last?
About 2 hours. 50 mg of caffeine peaks near 46 mg 45 minutes after you take it, halves every 5.7 hours, and falls below the 40 mg sleep threshold about 2 hours later.
| Peak level, 45 minutes in | 46 mg |
| Time to fall below 40 mg | 2 hours |
| Left after 6 hours | 25 mg |
| Left after 12 hours | 12 mg |
| Latest hour for an 11 pm bedtime | 8:58 pm |
| Share of the 400 mg daily limit | 12% |
Hour by hour
| Time after the dose | If taken at 8 am | Still active | For sleep |
|---|---|---|---|
| 1 hour | 9 am | 45 mg | still working |
| 2 hours | 10 am | 40 mg | still working |
| 4 hours | 12 pm | 31 mg | clear |
| 6 hours | 2 pm | 25 mg | clear |
| 8 hours | 4 pm | 19 mg | clear |
| 10 hours | 6 pm | 15 mg | clear |
| 12 hours | 8 pm | 12 mg | clear |
| 16 hours | 12 am | 7 mg | clear |
| 24 hours | 8 am | 3 mg | clear |
What 50 mg looks like
Fifty milligrams is a cup of black tea or a can of Mountain Dew. It sits below the 75 mg at which the European Food Safety Authority accepts a measurable effect on attention, so many people will not notice it at all.
What makes 50 mg worth tracking is that it rarely arrives alone. On top of a morning coffee that has not cleared, it is enough to push the total back over the 40 mg line. That is how an afternoon tea ends up costing sleep that the tea alone never could.
One serving of these holds about 50 mg: ristretto (44 mg), black tea (48 mg), Mountain Dew (50 mg).
| Drink | One serving | To reach 50 mg |
|---|---|---|
| Filter coffee | 96 mg per 8 oz cup | 0.5 |
| Espresso | 64 mg per 1 oz shot | 0.8 |
| Black tea | 48 mg per 8 oz cup | 1 |
| Red Bull | 80 mg per 8.4 oz can | 0.6 |
| Coca-Cola | 32 mg per 11.2 oz can | 1.6 |
How late can you take it?
Count back 2 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 50 mg |
|---|---|
| 9 pm | 6:58 pm |
| 9:30 pm | 7:28 pm |
| 10 pm | 7:58 pm |
| 10:30 pm | 8:28 pm |
| 11 pm | 8:58 pm |
| 11:30 pm | 9:28 pm |
| midnight | 9:58 pm |
| 1 am | 10:58 pm |
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 | 1 and a half hours | 9:28 pm |
| Average | 5.7 hours | 2 hours | 8:58 pm |
| Slow | 7.9 hours | 2 and a half hours | 8:17 pm |
Common questions
How long does 50 mg of caffeine last?
About 2 hours for an average adult. 50 mg peaks near 46 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 50 mg of caffeine a lot?
No. 50 mg is a small dose, about a cup of black tea. It is 12% of the 400 mg daily limit for a healthy adult.
How late can I take 50 mg of caffeine and still sleep?
For an 11 pm bedtime the latest is 8:58 pm. Move it by the same amount as your own bedtime. People who clear caffeine slowly need about 2 and a half hours, so they should stop earlier still.
How much of a 50 mg dose is left after 12 hours?
About 12 mg, for an average adult. After 6 hours about 25 mg is still active, and after 24 hours about 3 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.
