Contoured 3D sleep mask
Best for: blocking light in rooms you cannot fully darken
Caffeine cutoff calculator
Find the latest time you can have caffeine and still sleep well.
How to read your result
- The cutoff combines all entered pre-bed drinks as a conservative total-dose estimate.
- Check the estimated total remaining at bedtime; about 50 mg is a rule of thumb, not a proven safe threshold.
- Include all drinks and supplements you use; this estimate cannot predict how caffeine affects your sleep.
Estimate your cutoff
Last caffeine by 5:52 PM
Have your last caffeine at or before this time and less than ~50 mg will still be in your body at bedtime. Around 50 mg (about half a cup of coffee) is roughly the level where caffeine can start to delay sleep and make it lighter.
At bedtime:
13 mg
✓ Under target, good for sleep
Target:
Under 50 mg
A practical rule of thumb, not a proven safe threshold.
The cutoff combines all entered pre-bed caffeine amounts as one conservative dose. Your actual caffeine total at bedtime also depends on when each drink was consumed and how quickly you clear caffeine.
Pregnancy, oral contraceptives, some medicines and liver disease can slow caffeine clearance.
As an Amazon Associate, Stacking Years earns from qualifying purchases. This does not affect our rankings.
View on Amazon
Pure Encapsulations Magnesium Glycinate
Best for: an evening routine
How we calculate this
How we calculate this
For each dose before bedtime: dose × 0.5^(hours elapsed / half-life), summed across doses. Doses after bedtime are excluded. A late-evening dose before an after-midnight bedtime is treated as occurring the previous evening.
The overall cutoff combines the entered pre-bed amounts as a single conservative dose and uses bedtime minus max(half-life × log₂(total dose ÷ 50), 0). The separate per-dose cutoff list uses the same rule for each drink. The 50 mg value is a practical rule of thumb, not a proven safe threshold. Drake et al. 2013 found 400 mg six hours before bed reduced sleep by about one hour (PMID 24235903). Gardiner et al. 2023 estimated a 107 mg coffee at least 8.8 hours before bed and a 217 mg pre-workout at least 13.2 hours before bed (PMID 36870101). Typical half-life is 3–7 hours (Institute of Medicine 2001; Nehlig 2018).
Related: Sleep setup guide · Sleep evidence · Caffeine review · Magnesium review
Frequently asked questions
Is 50 mg a proven safe bedtime threshold?
No. It is a practical rule of thumb used here to calculate a cutoff, not a validated threshold for everyone.
Why does caffeine affect people differently?
Caffeine clearance varies. Pregnancy, oral contraceptives, some medicines and liver disease can slow it; the calculator lets you compare 3-, 5- and 7-hour half-lives.
Does the estimate include every source of caffeine?
Only the doses you enter. Check labels for coffee, tea, energy drinks, chocolate, medicines and pre-workout products.
What if I have a sleep problem?
A calculator cannot diagnose insomnia or sleep apnea. Persistent sleep problems are worth discussing with a clinician.
Not medical advice. Talk to your doctor or pharmacist before starting supplements, especially if you take medication, are pregnant or have a health condition.