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Calcimator

Caffeine Half-Life Calculator

Calculate how much caffeine remains in your system at bedtime and when to stop drinking coffee.

Inputs

mg

Results

Caffeine at Bedtime

57 mg

Sleep Disruption RiskYes — Above threshold
Latest Safe Coffee Time11:23
Your Caffeine Half-Life5 hrs
Hours to Safe Level11.6 hrs
Hours Until Bedtime9 hrs
How to Use This Calculator
  1. Enter the total milligrams of caffeine consumed today.
  2. Set your consumption time using the hour and minute fields.
  3. Input your target bedtime hour.
  4. Review Caffeine at Bedtime in mg to see how much will still be in your system when you sleep.
  5. Adjust your last caffeine cutoff time until the bedtime level drops below 50 mg for minimal sleep disruption.

How the result changes with Bedtime (24h)

Bedtime (24h)Caffeine at Bedtime
2176 mg
2266 mg
2450 mg
2544 mg

What each input means

Caffeine Amount
Caffeine consumed (coffee ~95mg, espresso ~63mg, tea ~47mg)
Consumption Time (24h)
Hour you consumed caffeine (24-hour)
Bedtime (24h)
Hour you plan to sleep (24-hour)
Caffeine Metabolism
How quickly your body processes caffeine

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Caffeine Amount = 200, Consumption Time (24h) = 14, Bedtime (24h) = 23, Caffeine Metabolism = 2 = 4 input(s) provided
  2. Calculate Caffeine at Bedtime
    Caffeine at Bedtime
    57 = 57
  3. Calculate Sleep Disruption Risk
    Yes — Above threshold = Yes — Above threshold
  4. Calculate Latest Safe Coffee Time
    Latest Safe Coffee Time = formatTime(safeHour
    11:23 = 11:23

Engine last updated . Checked against 3 independently-derived tests — how we verify calculators.

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