01
Choose the closest drink
Use the familiar drink cards first. If you have a specific canned beverage, enter the exact milligram label amount.
SLEEP SCIENCE · CIRCADIAN CUTOFF TOOL
Plan Your Last Caffeine with Precision.
Select your beverage, set when you finished your last sip, and map your biological caffeine clearance curve before bedtime.
1. Choose Drink
2. Set Finish Time
3. View Bedtime mg
STEP 1 · WHAT DID YOU DRINK?
Start with the closest match. You can edit it.
These are starting estimates, not promises about a specific drink. Packaged products vary—use the label when you have it. Why the range is wide →
STEP 2 · WHEN?
Your estimate at bedtime
26mg
About 29% of this coffee remains after 9 h.
remainingfrom 90 mg
A simple planning cutoff
1:46 PM
To model below 25 mg at bedtime: 9.2 hours earlier.
What to try next
Keep bedtime fixed. Move this drink earlier.
Use the calculator as a timing experiment for two weeks, not a diagnosis or a medical clearance.
YOUR ESTIMATED DECAY
This line updates as you change the drink, time, or clearance speed.
5-hour half-life
● Gold dot: your bedtime estimate– – 25 mg: planning lineVertical scale: 0–200 mg
YOUR EVENING TIMELINE
A visual check on how this drink fits before bed.
Lands after the planning cutoff
CIRCADIAN HYGIENE EXPERIMENT
Keep Bedtime Steady. Shift One Drink Earlier.
02
Set a realistic bedtime
The goal is understanding how adenosine receptor saturation affects Stage 3 & 4 restorative delta sleep.
03
Try one change at a time
Shift your final afternoon coffee 90 minutes earlier for 10 days. Observe deep sleep tracking and morning clarity.
This model uses a population average 5-hour half-life curve. Individual metabolic rates vary by CYP1A2 gene alleles, oral contraceptives, and liver transit.
Explore Dayspan Glycine →