Coffee & the nightcap
The two things you drink to get through the day and wind down at night are the same two things quietly taking your sleep apart — and you can't feel either one doing it.
Tell us what you actually drank. We'll tell you what it's doing to tonight, and exactly when to stop.
Caffeine cutoff
Add the coffees, teas and energy drinks you had today. We model how much is still in your blood at bedtime — and the last safe time for one more.
Add a drink to see the damage.
Why a 4pm coffee is still awake at midnight
Caffeine doesn't give you energy. It hides the fact that you're tired.
All day, a molecule called adenosine builds up in your brain. It's the body's sleep-pressure gauge — the longer you're awake, the more of it accumulates, and the heavier your eyes feel. Caffeine works by jamming into the same receptors adenosine uses, so the gauge stops reading. The tiredness is still there. You just stop feeling it.
The problem is the timing. Caffeine has a half-life of roughly five hours in an average adult — meaning five hours after that coffee, half of it is still in your bloodstream. After ten hours, a quarter. A 145 mg cup at 4pm leaves around 70 mg working at 9pm and 35 mg past midnight. That's enough to keep the adenosine gauge partly jammed while you're trying to sleep.
This is the part most people miss. Even when caffeine doesn't stop you dropping off, it suppresses slow-wave sleep — the deep stage where physical recovery happens. In controlled studies, a large dose taken a full six hours before bed still measurably cut total sleep time. The night looked normal. The recovery wasn't there.
How fast you clear it is also partly genetic. Some people carry a "fast metaboliser" liver enzyme and can have an espresso after dinner with no effect. Others — slow metabolisers, anyone pregnant, anyone on certain medications — hold onto caffeine far longer. If a late coffee wrecks you and barely touches your friend, that's not in your head. It's in your liver.
How much caffeine is actually in it
US serving sizes have crept up, so the numbers are higher than most people guess. Rough averages:
| Drink | Typical US size | Caffeine |
|---|---|---|
| Brewed / drip coffee | 12 oz | ≈ 145 mg |
| Espresso | 1 oz shot | ≈ 65 mg |
| Latte / cappuccino | 2 shots | ≈ 130 mg |
| Cold brew | 16 oz | ≈ 205 mg |
| Large coffeehouse drip | 16 oz | ≈ 310 mg |
| Black tea | 8 oz | ≈ 47 mg |
| Green tea / matcha | 8 oz | ≈ 30–65 mg |
| Energy drink | 8–16 oz | ≈ 80–160 mg |
| Pre-workout | 1 scoop | ≈ 150–300 mg |
| Cola | 12 oz | ≈ 35 mg |
What to do tonight
- Treat your bedtime as fixed, then count back. For most people, the last caffeine of the day should land 8–10 hours before bed; six hours is the floor, not the target.
- If you're a slow metaboliser or sleep lightly, move your cutoff to lunchtime. An 11am espresso is a different drink from a 3pm one.
- Watch the hidden sources — pre-workout, "decaf" that isn't, dark chocolate, some painkillers. They count.
- Don't fix a bad night with a bigger morning coffee. That deepens the adenosine debt and pushes the cycle into tomorrow night.
Alcohol cutoff
Add tonight's drinks in real glasses — a bottle of beer, a restaurant pour of wine, a cocktail. We convert them to standard drinks and tell you when to stop.
Add a drink to see how it splits your night.
Why a nightcap is the worst kind of sleep aid
It knocks you out fast — then takes the second half of your night as payment.
Alcohol is a sedative. It quietens the nervous system, which is why a drink or two makes you feel like you're falling asleep faster. That part is real, and it's exactly why so many people use it to wind down. The catch is what happens after you're asleep.
As your body metabolises the alcohol over the next few hours, the sedation lifts and the system rebounds the other way. Your brain pushes back toward alertness, your heart rate rises, and the sleep you get in the back half of the night turns shallow and broken — more awakenings, lighter stages, the 3am stare at the ceiling. The first half feels like sleep. The second half barely is.
It does a few other things on the way through. It relaxes the muscles around your airway, so snoring and breathing pauses get worse — even in people who don't normally have them. It's a diuretic, which is the real reason for the middle-of-the-night bathroom trip. And it suppresses REM sleep, the stage tied to memory and emotional processing, which is part of why you can sleep eight hours after drinking and still wake up foggy and flat.
What counts as one drink
A US standard drink is about 14 grams of pure alcohol. The trap is that real glasses rarely match it — a craft IPA or a generous restaurant pour is closer to two.
| Drink | Real-world size | Standard drinks |
|---|---|---|
| Regular beer (5%) | 12 oz bottle | 1.0 |
| Craft IPA (7%) | 16 oz can | ≈ 1.9 |
| Wine (12%) | 5 oz pour | 1.0 |
| Wine, restaurant pour (13%) | 8 oz | ≈ 1.7 |
| Spirit (40%) | 1.5 oz shot | 1.0 |
| Cocktail (2 shots) | — | ≈ 2.0 |
| Hard seltzer (5%) | 12 oz | 1.0 |
Your body clears roughly one standard drink an hour — slower if you're smaller, faster if you're larger, but one an hour is a fair planning rule. Three drinks means about three hours of processing before your body is even back to baseline.
What to do tonight
- Stop drinking early enough that you're back to baseline well before bed — aim for your last drink to clear about two hours before you sleep.
- Front-load the night, not the end of it. A drink with dinner does far less damage than one right before bed.
- Match alcohol with water through the evening to blunt the diuretic effect and the wake-ups.
- If you're drinking to fall asleep, that's the signal worth paying attention to — the thing that gets you down isn't the thing that keeps you down.
So, tonight
Set your cutoff
Count back from bedtime and draw a hard line on your last coffee. Earlier than feels necessary.
Finish early
Get your last drink in with enough runway to clear before bed, and keep water alongside it.
Built for recovery, not sedation
The reason people reach for a nightcap is that they want something to switch them off. Moongreens does the opposite of knocking you out — it's a melatonin-free night drink that supports the systems caffeine and alcohol disrupt, so the sleep you get is the kind you actually recover from. Manufactured in the USA. The first thirty people we gave it to all said it tastes great.
Try Moongreens →Thirty nights isn't long enough to judge a recovery formula — so it comes with a 90-night guarantee. Enough time to feel the difference in how you wake up, not just how you fall asleep.
This calculator is for general information and isn't medical advice. Caffeine and alcohol affect everyone differently. If you're pregnant, take medication, or have a health condition, talk to your doctor before making changes.