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Both calculators run independently — change the inputs on either side to compare results.

Caffeine Sleep Impact Calculator

Calculate how many milligrams of caffeine remain active in your system at bedtime based on when and how much you consumed, using a standard 5-hour half-life. Even moderate residual caffeine at bedtime measurably disrupts sleep architecture, not just sleep onset.

Caffeine Consumption Time (hours (24h format))

Caffeine Amount (mg)

Desired Bedtime (hours (24h format))

Fill in the required fields to see your result.

Sleep

REM Sleep Calculator

Estimate how much of your nightly sleep is spent in REM based on total sleep time and age. REM sleep is critical for memory consolidation, emotional processing, and creative problem-solving, and is the first stage to be cut short by sleep restriction.

Total Sleep Time (hours)

Age (years)

Fill in the required fields to see your result.

Key differences

	Caffeine Sleep Impact Calculator	REM Sleep Calculator
Category	Sleep	Sleep
Inputs required	3	2
Result	Caffeine Remaining at Bedtime (mg)	Estimated REM Sleep (hours)
What it does	Calculate how many milligrams of caffeine remain active in your system at bedtime based on when and how much you consumed, using a standard 5-hour half-life. Even moderate residual caffeine at bedtime measurably disrupts sleep architecture, not just sleep onset.	Estimate how much of your nightly sleep is spent in REM based on total sleep time and age. REM sleep is critical for memory consolidation, emotional processing, and creative problem-solving, and is the first stage to be cut short by sleep restriction.