Calculator
Caffeine Cut-Off Calculator
The “no coffee after 2pm” rule is too generic — it ignores dose and personal metabolism. This calculator tells you the latest time you can have a given dose without leaving meaningful caffeine in your system at bedtime.
Tap to set dose
Cut-off times for this dose
Strict cut-off (below 30mg at bed)
2:41pm
Caffeine effect should be negligible. ~8.3h before bed.
Practical cut-off (below 100mg at bed)
11:00pm
Some sleep impact possible but moderate. ~0.0h before bed.
How it works
We invert the standard half-life decay equation: given your target bedtime and the dose you're about to consume, we solve for the time that leaves below 30mg in your system at bedtime (the “strict” cut-off, where caffeine is effectively background) and below 100mg (the “practical” cut-off, where sleep impact is moderate).
Half-life varies enormously by individual. Genetics alone can shift it by a factor of 5×. The “average” option here uses 5 hours; slow metabolisers should be conservative.