Caffeine Kick-Down Calculator
Drank coffee too late? Find out how much caffeine will still be in your system by bedtime and if it might affect your sleep.
Your Caffeine at Bedtime
Caffeine Remaining
0
mg
This amount is unlikely to affect your sleep.
What is Caffeine Half-Life?
"Half-life" is the time it takes for the initial amount of a substance in your body to be reduced by half. For caffeine in healthy adults, the average half-life is **about 5 to 6 hours**.
This means if you drink a coffee with 100 mg of caffeine at 2:00 PM:
- By **8:00 PM** (6 hours later), you'll still have **50 mg** in your system.
- By **2:00 AM** (another 6 hours), you'll still have **25 mg** remaining.
This calculator uses this 6-hour half-life average to estimate how much caffeine is left in your body when you're trying to sleep.
How Caffeine Affects Your Sleep (and Blood Sugar)
Caffeine works by blocking adenosine, a brain chemical that makes you feel sleepy. While this is great in the morning, having caffeine in your system at night can seriously disrupt your sleep architecture.
- Disrupts Deep Sleep: Even small amounts of caffeine (like the 50 mg left at 8 PM) can reduce the amount of restorative deep sleep you get.
- Impacts Blood Sugar: Poor sleep is directly linked to higher **blood sugar** levels and insulin resistance. Caffeine itself can also blunt insulin sensitivity in some people.
- Creates a Vicious Cycle: You sleep poorly due to caffeine, wake up tired, and drink even more caffeine to compensate, further disrupting your next night's sleep.
How to Use This Calculator
1. Select Your Drink: Choose your beverage from the list. The values are based on common averages.
2. Set Quantity & Time: Enter how many servings you had and what time you drank it.
3. Set Your Bedtime: Enter your usual bedtime.
The calculator will show you how many milligrams (mg) of caffeine are estimated to be in your system at bedtime and provide a warning based on the amount. Generally, experts recommend having **less than 50 mg** of caffeine in your system (or stopping caffeine 6-8 hours) before sleep.
Common Caffeine Content
| Drink (Serving Size) | Caffeine (mg) |
|---|---|
| Brewed Coffee (8 oz / 240ml) | ~95 mg |
| Espresso (1 shot / 30ml) | ~64 mg |
| Energy Drink (Monster, 16 oz / 473ml) | ~160 mg |
| Black Tea (8 oz / 240ml) | ~47 mg |
| Green Tea (8 oz / 240ml) | ~28 mg |
| Cola (12 oz / 355ml) | ~34 mg |
| Decaf Coffee (8 oz / 240ml) | ~2-5 mg |