Caffeine: the dose and the bill
The most effective legal performance drug there is, with a half-life long enough to still be in you at bedtime. Here is how to use it, and what it quietly costs.
Founder of Vertex Strength LabPublished · Updated
Short answer
The effective pre-workout caffeine dose is 3 to 6 mg per kilogram of bodyweight, about 240 to 480 mg for an 80 kg lifter, taken 45 to 60 minutes before training. Start at 3 mg/kg. With a half-life of about five hours, stop caffeine at least eight hours before bed, because it disrupts sleep even when you cannot feel it.
Caffeine is the only supplement in most people's stack that they would notice missing within a day. It is also the one they think least carefully about, because it arrives as a beverage rather than a dose.
Used deliberately it improves strength, endurance and how hard a session feels. Used carelessly it borrows performance from tomorrow.
3–6 mg/kg
The performance dose — around 240–480 mg for an 80 kg lifter
~5 h
Half-life — half of it is still circulating five hours later
What it actually does: how caffeine improves training
Caffeine blocks adenosine receptors. Adenosine accumulates through the day and is part of how your brain registers fatigue, so blocking it does not create energy — it suppresses your perception of not having any.
That distinction matters, because it explains the pattern of the benefits.
Where caffeine helps most.
relative size of the performance benefit
Perceived exertion
how hard it feels
Large
Muscular endurance
reps at a given load
Solid
Endurance performance
time trials
Solid
Maximal strength
1RM
Small
Power output
jumps, sprints
Small–moderate
The largest and most reliable effect is on how hard training feels. That is not a trivial benefit — a session that feels 10% easier is a session where you do the last two sets properly instead of cutting them.
45 min
Plasma caffeine peaks roughly 30 to 60 minutes after ingestion. Taking it as you walk into the gym means it arrives for your third exercise. Take it before you leave the house.
The dose, in real units: coffee, tea and pre-workout
The research dose of 3–6 mg per kilogram (Guest et al. 2021) sounds abstract until you convert it into things people actually drink.
Caffeine, in ordinary objects.
~95 mg
A standard mug of filter coffee
Highly variable — anywhere from 70 to 140 mg depending on bean, grind and brew. Coffee is the least precise delivery method there is.
~65 mg
A double espresso
Less than most people assume. Espresso is concentrated, not large.
~50 mg
A mug of black tea
Around half a coffee. Green tea is lower again, roughly 30 mg.
~200 mg
A typical pre-workout scoop
Often more. This is where accidental over-dosing happens, particularly when it lands on top of a normal coffee day.
200 mg
A caffeine tablet
The only precise option. Unglamorous, cheap, and the sensible choice if you are actually dosing rather than drinking.
Starting at the low end is genuinely worth doing. The dose-response for performance flattens out well before the dose-response for jitteriness, anxiety and a wrecked night does.
The bill arrives at bedtime: caffeine and sleep
Here is the part that gets ignored. Caffeine's half-life is around five hours, with wide individual variation — some people clear it in three, some in seven or more.
Where it is at bedtime.
2pm
300 mg
Pre-workout dose. Peaks around 3pm, session feels great.
7pm
150 mg
One half-life in. Still roughly a strong coffee's worth circulating, and you no longer notice it because you are habituated.
midnight
75 mg
Bedtime. A cup of tea's worth of adenosine blockade, sitting between you and deep sleep.
5am
37 mg
And you wake up tired, and the fix is a coffee. This is the loop.
The finding worth internalising is that people are bad judges of this. In controlled conditions (Drake et al. 2013), a dose taken six hours before bed reduced sleep meaningfully in participants who did not report feeling affected. "It doesn't keep me awake" is not evidence.
"Caffeine doesn't affect my sleep, I can drink it at 8pm."
You just can't feel it
Given that sleep is one of the more powerful recovery variables available to a lifter, a habit that trades an hour of it for a slightly better evening session is a bad trade made invisibly.
Tolerance, and whether to cycle
Tolerance to caffeine's alertness effects develops quickly. Tolerance to the performance effects appears to develop less completely — habitual users still get an ergogenic benefit, though probably a smaller one.
Whether to periodically abstain is genuinely unsettled. A pragmatic approach: keep your baseline daily intake modest, and reserve the larger deliberate doses for sessions where they matter. That way there is somewhere to go.
Using it well
- Take it 45–60 minutes before you train, not on arrival.
- Start at 3 mg/kg. Move up only if the low dose does nothing.
- Set a cut-off at least eight hours before bed. For most people that means nothing after early afternoon.
- Count your total. Pre-workout plus two coffees plus a green tea adds up faster than anyone tracks.
- Skip it on easy days. Keeps tolerance down and gives it somewhere to work.
Key numbers
| What | Number |
|---|---|
| Performance dose | 3–6 mg/kg (240–480 mg at 80 kg) |
| When to take it | 45–60 min before training |
| Half-life | About 5 hours, 3 to 7+ between people |
| Last dose | At least 8 hours before bed |
| Daily upper limit for healthy adults | 400 mg |
| Mug of filter coffee | About 95 mg |
The short version
Caffeine is the most effective legal performance aid available, it works best on how hard training feels, and 3–6 mg/kg an hour beforehand is the dose.
Then respect the half-life. A pre-workout at 6pm is still with you at midnight, and the sleep it costs is worth more to your training than the session it improved.
Common questions
How long before a workout should I take caffeine?
45 to 60 minutes before. Blood levels peak roughly 30 to 60 minutes after you take it, so taking it as you walk into the gym means it arrives partway through the session.
How much caffeine is in a cup of coffee?
About 95 mg in a standard mug of filter coffee, though anywhere from 70 to 140 mg is normal. A double espresso is about 65 mg and a mug of black tea about 50 mg.
Does caffeine increase strength?
A little. Its largest and most reliable effect is on how hard training feels, with solid effects on muscular endurance and smaller ones on maximal strength.
Should I cycle off caffeine?
The evidence is unsettled. Tolerance to the alertness effect builds quickly, while the performance effect fades less completely. A pragmatic approach is a modest daily baseline, with larger doses saved for sessions that matter.
Can I drink coffee in the evening if it does not keep me awake?
Better not. In controlled work, 400 mg taken six hours before bed measurably reduced sleep, including in people who reported no effect. Habituation dulls the feeling, not the pharmacology.
References
- Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition. 2021;18(1). doi:10.1186/s12970-020-00383-4
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed. J Clin Sleep Med. 2013;9(11):1195–1200. doi:10.5664/jcsm.3170