Compare calculators

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

Sleep Cycle Calculator

Find your ideal bedtime by working backward from your wake-up time in complete 90-minute sleep cycles. Waking at the end of a cycle (rather than mid-cycle) leaves you feeling more refreshed than the same total hours timed less carefully.

Desired Wake Time (hours (24h format))

Number of Sleep Cycles (cycles)

Fill in the required fields to see your result.

Key differences

	Caffeine Sleep Impact Calculator	Sleep Cycle Calculator
Category	Sleep	Sleep
Inputs required	3	2
Result	Caffeine Remaining at Bedtime (mg)	Optimal Bedtime (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.	Find your ideal bedtime by working backward from your wake-up time in complete 90-minute sleep cycles. Waking at the end of a cycle (rather than mid-cycle) leaves you feeling more refreshed than the same total hours timed less carefully.