Caffeine Cut-Off Calculator: When to Stop Coffee Before Bed

When should you stop drinking caffeine before bed?

For most adults, the last caffeine of the day should be 8 to 10 hours before bedtime if you want less than a quarter of it left when you lie down. Caffeine has an average half-life of about five hours, so a 3 pm coffee still leaves roughly a third of its caffeine in your blood at 11 pm. The one sleep-laboratory study that tested timing directly gave people 400 mg of caffeine (about four cups of coffee) at bedtime, three hours before, and six hours before. Even the six-hour dose cut their measured sleep by more than an hour, and most of them did not notice the difference.

The calculator above does the arithmetic for your own numbers: your bedtime, what you drank, when you drank it, and how quickly your body clears caffeine.

How the calculator works

• The curve. Caffeine leaves the body by halves. After one half-life, half the dose is gone; after two, three quarters; after three, seven eighths. The chart plots that curve from your last drink to bedtime and beyond.
• The half-life. Five hours is the adult average, but the published range runs from about 1.5 to 9.5 hours. Smokers clear caffeine faster. Pregnancy, oral contraceptives, some antidepressants and liver conditions slow it down, in some cases to ten hours or more. Pick the setting that matches you.
• The two cut-off times. They are planning marks, not medical limits: the latest you could have the same drink and still have under a quarter, or under a tenth, of it left at bedtime. Many people sleep well with more than that in their system. If you do not, these are the times to try.
• The drink amounts. Typical figures from the US Food and Drug Administration and Mayo Clinic tables. Real cups vary a lot: a 16 oz coffee-shop brew can carry 300 mg, and espresso drinks depend on the number of shots. When you know the number from the label or the cafe, type it in.

Caffeine in common drinks

What changes how fast you clear caffeine

Caffeine is broken down almost entirely by one liver enzyme, CYP1A2. How active that enzyme is explains most of the difference between the friend who sleeps after an espresso and the one who is awake until two.

• Genetics. Common variants in the CYP1A2 gene split people into faster and slower metabolisers.
• Smoking induces the enzyme and roughly halves caffeine's half-life. People who quit often find their usual coffee suddenly feels much stronger.
• Pregnancy slows clearance progressively; by the third trimester the half-life can be two to three times longer than usual.
• Oral contraceptives that contain estrogen roughly double the half-life.
• Some medications, including the antidepressant fluvoxamine and some antibiotics, block the enzyme. Liver disease also slows clearance.

Three habits that work with the number

1. Fix a cut-off time and keep it. The calculator gives you one; put it in your phone. A consistent cut-off is easier to keep than a daily judgement call.
2. Swap the afternoon cup, do not skip it. Decaf carries 2 to 5 mg, green tea about 28 mg. The ritual of the cup survives; the caffeine mostly does not.
3. Run the evening the same way every night. Caffeine timing fixes one input. A repeatable wind-down fixes the rest. Sleep is a sequence, not a switch explains the 60-30-15 evening Veluna is built around.

Sources

1. Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine. 2013;9(11):1195-1200.
2. Institute of Medicine, Committee on Military Nutrition Research. Caffeine for the Sustainment of Mental Task Performance. National Academies Press; 2001. Chapter 2, pharmacology of caffeine.
3. US Food and Drug Administration. Spilling the Beans: How Much Caffeine is Too Much? Consumer update.
4. Mayo Clinic. Caffeine content for coffee, tea, soda and more.
5. Parsons WD, Neims AH. Effect of smoking on caffeine clearance. Clinical Pharmacology and Therapeutics. 1978;24(1):40-45.
6. Knutti R, Rothweiler H, Schlatter C. Effect of pregnancy on the pharmacokinetics of caffeine. European Journal of Clinical Pharmacology. 1981;21(2):121-126.
7. Abernethy DR, Todd EL. Impairment of caffeine clearance by chronic use of low-dose oestrogen-containing oral contraceptives. European Journal of Clinical Pharmacology. 1985;28(4):425-428.

These studies looked at caffeine, sleep and the liver enzyme that clears caffeine in general populations. None of them tested a Veluna product; this page relates to individual ingredients and habits and is not the Veluna product.