Caffeine Calculator
How long caffeine stays in your system, by drink and time consumed
Caffeine Decay Calculator
Total: 95mg caffeine
How sensitive are you to caffeine?
Not sure? Choose “Average.” If afternoon coffee keeps you awake at night, choose “Very sensitive.”
Caffeine now
93mg
98% remaining
At bedtime
6mg
Below sleep-disruption threshold
Under 50mg by
7:06 am
Approximate clearance time
Caffeine decay curve (mg remaining over time)
Based on 5-hour half-life (average adult). Individual variation: 1.5 to 9.5 hours.
Half-life range 1.5 to 9.5 hours per Nehlig et al. (1992) and FDA (2023). This tool is for informational purposes only, not medical advice.
How this calculator works
This calculator uses the standard caffeine decay formula: C(t) = C0 x (0.5)^(t / half-life), where C0 is the initial caffeine dose, t is hours elapsed, and half-life is your estimated caffeine half-life.
The default half-life is 5 hours, which is the average for healthy adults per FDA guidance (2023) and Nehlig et al. (1992). The actual range is 1.5 to 9.5 hours depending on genetics (CYP1A2 gene), liver function, medications, and pregnancy.
Caffeine values in the drink database are sourced from published nutrition data (USDA FoodData Central, FDA, and brand nutrition pages). Every value has a source and date. This tool is for informational purposes only, not medical advice.
Caffeine database: published values
Every value below is sourced from published nutrition data. No invented numbers.
Caffeine content varies by preparation method, brand, and batch. Values above are published estimates, not guarantees.
Why matcha feels different from coffee at the same caffeine dose
Matcha contains L-theanine alongside caffeine. Research by Haskell et al. (2008, Psychopharmacology) found that the caffeine plus L-theanine combination produces calmer, steadier alertness compared to caffeine alone. L-theanine does not change the half-life or the total caffeine load, but it modulates the experience: gentler onset, less jitteriness, and a more gradual energy taper.
This is why many people who switch from coffee to matcha report less of a crash, even at similar caffeine doses. The adenosine rebound still happens, but the lower typical dose (70mg vs 95 to 200mg in coffee) means less adenosine accumulates, and the rebound is gentler.
Caffeine calculator: frequently asked questions
How long does caffeine stay in your system?
Caffeine has a half-life of approximately 5 hours in healthy adults, meaning half of the caffeine is eliminated every 5 hours. The full range is 1.5 to 9.5 hours depending on genetics (CYP1A2 gene), liver function, medications, and pregnancy. A 200mg dose at 8am leaves roughly 100mg at 1pm, 50mg at 6pm, and 25mg at 11pm for an average metabolizer.
Source: Nehlig et al., Neuroscience and Biobehavioral Reviews (1992); FDA (2023).
What is caffeine half-life?
Half-life is the time it takes your body to eliminate half of a substance. For caffeine, the average half-life in healthy adults is 5 hours. This means if you consume 100mg of caffeine, 50mg remains after 5 hours, 25mg after 10 hours, and 12.5mg after 15 hours. The half-life is the same regardless of the source: coffee, matcha, tea, or energy drinks.
Source: Nehlig et al., Neuroscience and Biobehavioral Reviews (1992).
How much caffeine is in matcha vs coffee?
A standard 2g matcha serving contains approximately 70mg caffeine. An 8oz drip coffee contains approximately 95mg. A Starbucks Grande latte contains approximately 150mg. The caffeine half-life is the same for all sources, but matcha also contains L-theanine, which research shows produces calmer, steadier alertness compared to caffeine alone.
Matcha caffeine: Kochman et al., Molecules (2021). Coffee: FDA (2023).
How long before bed should I stop drinking caffeine?
For most people, stopping caffeine 6 hours before bedtime is a reasonable guideline. With a 5-hour half-life, a 200mg dose consumed 6 hours before bed leaves roughly 50mg at bedtime. If you are a slow metabolizer (half-life up to 9.5 hours), you may need to stop 8 to 10 hours before bed. Research by Drake et al. (2013) found that caffeine consumed 6 hours before bed significantly reduced sleep quality.
Source: Drake et al., Journal of Clinical Sleep Medicine (2013).
What is the adenosine rebound (caffeine crash)?
Caffeine works by blocking adenosine receptors, not by destroying adenosine. Adenosine continues to accumulate while you are caffeinated. When caffeine clears your system, all that accumulated adenosine suddenly has access to its receptors, causing a rapid drop in energy. This is the mechanism behind the afternoon crash. Lower caffeine doses produce less adenosine accumulation and a gentler rebound.
Source: Fredholm et al., Pharmacological Reviews (1999).
Does body weight affect caffeine metabolism?
Body weight affects the volume of distribution (how caffeine is distributed through body tissues) but has a relatively small effect on the half-life for most adults. The primary determinants of caffeine half-life are genetics (CYP1A2 gene variant), liver function, medications (some antibiotics and antidepressants slow caffeine metabolism), and pregnancy (half-life can extend to 15 hours or more in the third trimester).
Source: Nehlig et al., Neuroscience and Biobehavioral Reviews (1992).
Is matcha caffeine different from coffee caffeine?
The caffeine molecule is identical regardless of source. What differs is the co-occurring compounds. Matcha contains L-theanine, which research shows modulates the caffeine effect: calmer alertness, less jitteriness, and a more gradual energy curve. The half-life is the same. The experience is different because of L-theanine, not because the caffeine itself is different.
Source: Haskell et al., Psychopharmacology (2008).
Want steady energy without the crash?
Steady Matcha is a single-origin ceremonial grade matcha with a published Eurofins COA. 70mg caffeine per 2g serving, plus L-theanine for a smoother curve.
Learn about Steady Matcha →