The blog
Caffeine, water & sleep.
Plain-English guides to what coffee, tea and energy drinks actually do in your body, with the studies behind every number.
Caffeine science
How Long Does Caffeine Last? Half-Life, Timeline and What Changes It
Caffeine peaks in under an hour but takes 5 hours to drop by half, and much longer if you're on the pill or pregnant. Here's the hour-by-hour timeline for a cup of coffee.
Sleep
When to Stop Drinking Coffee Before Bed (By Dose, Not Guesswork)
"No coffee after 2 pm" is too simple. The right caffeine cutoff depends on how strong the drink is and how fast you clear it. Here's a cutoff table for common drinks, backed by sleep studies.
Hydration
Does Coffee Dehydrate You? What the Research Actually Says
Coffee is a mild diuretic, but for regular drinkers a normal cup hydrates about as well as water. Here's what the studies show, where the myth came from, and when caffeine does make you pee more.
Caffeine science
How Much Caffeine Is Too Much? Daily Limits, Signs and Safe Doses
The FDA says up to 400 mg of caffeine a day is fine for most adults, but that number hides a lot. Here's what 400 mg looks like in real drinks, who needs less, and the signs you've had too much.
Hydration
How Much Water Should You Drink a Day? (It's Not Always 8 Glasses)
The "8 glasses a day" rule has no solid science behind it. Here's what the official guidelines say, how to work out your own daily water goal from your weight and activity, and whether coffee counts.
Pregnancy
Caffeine and Pregnancy: The 200 mg Limit, Explained
Most guidelines say to keep caffeine under 200 mg a day in pregnancy. Here's what that means in real drinks, why caffeine lasts up to three times longer when you're pregnant, and how to stay under the limit.
Caffeine chart
Caffeine Content Chart: Coffee, Tea, Soda and Energy Drinks
How much caffeine is in an espresso, a grande, a can of Monster or a cup of green tea? A side-by-side chart of popular drinks by size, with what each one means for your daily limit and your sleep.
Sleep
How Caffeine Affects Sleep, Even When You Fall Asleep Fine
Caffeine doesn't just keep you awake. It cuts deep sleep, delays your body clock and costs you about 45 minutes a night, often without you noticing. Here's how it works and how to keep coffee without losing sleep.
Know before you drink.
Caffeine vs Water shows what your next coffee will do to your sleep, and keeps your water on pace. For iPhone and Apple Watch. No account, no ads.
Coming soon to the App Store