Caffeine in mg — the real numbers for every drink and supplement
The FDA lists 400 mg/day as safe for healthy adults. A large drip coffee is 200 mg; a pre-workout scoop is 200–400 mg; an energy drink 80–300 mg. Stacking any two easily exceeds the daily cap — this is where insomnia, palpitations, and anxiety start.
Caffeine content varies wildly by brew method, brand, and serving size. Marketing labels often quote 'per 8 fl oz' when the actual can is 16 fl oz. Real numbers below are per typical serving, cross-checked against USDA FoodData Central and manufacturer spec sheets.
Reference table — caffeine per serving
| Drink | Serving | Caffeine (mg) | |---|---|---| | Drip coffee | 8 fl oz (237 mL) | 95 | | Drip coffee, Starbucks Pike | 16 fl oz (grande) | 310 | | Espresso shot | 1 fl oz (30 mL) | 63 | | Double espresso | 2 fl oz (60 mL) | 125 | | Cold brew concentrate | 8 fl oz | 200 | | Instant coffee | 8 fl oz | 65 | | Decaf coffee | 8 fl oz | 2 | | Black tea | 8 fl oz | 47 | | Green tea | 8 fl oz | 28 | | Matcha, ceremonial | 1 tsp (2 g) | 70 | | Yerba mate | 8 fl oz | 78 | | Red Bull | 8.4 fl oz (250 mL) | 80 | | Monster Energy | 16 fl oz | 160 | | Bang | 16 fl oz | 300 | | Celsius | 12 fl oz | 200 | | Coca-Cola | 12 fl oz | 34 | | Diet Coke | 12 fl oz | 46 | | Mountain Dew | 12 fl oz | 54 | | Dark chocolate 70% | 30 g | 24 | | Milk chocolate | 30 g | 6 | | Pre-workout (C4 Original) | 1 scoop | 150 | | Pre-workout (Bucked Up) | 1 scoop | 200 | | Pre-workout (Total War) | 1 scoop | 320 | | No-Doz / caffeine pill | 1 tablet | 200 |
Safe intake limits by source
**FDA (US):** 400 mg/day for healthy adults. Single dose <200 mg to avoid acute cardiovascular strain.
**EFSA (EU, 2015):** 400 mg/day habitual, 200 mg single dose. 200 mg 2 hours pre-sleep still detectable in adult sleep architecture.
**Pregnancy:** ACOG 200 mg/day cap — one grande drip coffee reaches this.
**Adolescents (12–18):** AAP recommends <100 mg/day. Energy-drink servings routinely exceed this in single cans.
**Cardiac patients:** individualised; often 200 mg/day cap.
Worked example — stacking caffeine
Typical morning:
- 08:00 – Starbucks grande drip: 310 mg
- 10:00 – pre-workout scoop (Bucked Up): 200 mg
- 12:00 – Diet Coke with lunch: 46 mg
- 15:00 – Red Bull: 80 mg
- **Total: 636 mg** — 59% above the FDA cap.
Every one of those is a common single-portion drink. Insomnia, jitters, and racing pulse follow. Cutting the pre-workout brings it under 500; also dropping the 15:00 Red Bull brings it to 356 — under cap and sleep-safe.
Half-life and sleep
Caffeine half-life is 4–6 hours in typical adults, up to 8 hours in slow metabolisers (CYP1A2 variants). A 200 mg dose at 15:00 leaves ~50–100 mg still active at 23:00. Even modest evening intake reduces slow-wave sleep by 15–25% (Drake et al., 2013). Cutoff time for good sleep: caffeine ≤ 100 mg after noon for slow metabolisers, ≤ 200 mg after 14:00 for fast.
Bean roast and caffeine — the myth
Light roast has slightly more caffeine per bean than dark; dark has more per volume (denser beans pack more per scoop). By weight of ground coffee, the difference is <5%. Both bean weight and grind size affect brew caffeine more than roast level. The 'dark roast has less caffeine' claim is a rounding error inflated by marketing.
Tolerance and withdrawal
Habitual users develop adenosine-receptor upregulation within 7–14 days, reducing perceived stimulation. Withdrawal after 100 mg+/day chronic intake: headache, fatigue, low mood, peaking 24–48 hours after last dose. Full CNS reset takes ~10 days. Cycling caffeine (5 on / 2 off, or 3-week resets) restores sensitivity.
Not just coffee — the L-theanine synergy
Tea contains L-theanine (~25 mg per 200 mL green tea), which blunts caffeine's cortisol spike and extends the alertness plateau. A cup of green tea at 28 mg caffeine + 25 mg L-theanine 'feels' longer-lasting than 28 mg from a Coke. Pre-workout blends increasingly add L-theanine (typically 100 mg per 200 mg caffeine) for this reason.
The five-second recap
Keep total daily caffeine under 400 mg (200 mg during pregnancy). One large drip coffee + one energy drink already exceeds it. Half-life is 5 hours — no meaningful caffeine after 14:00 for sleep-sensitive adults.
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FAQ
How much caffeine is in a Starbucks drink?+
Grande (16 fl oz) drip Pike Place: 310 mg. Grande latte: 150 mg. Grande cold brew: 205 mg. Espresso shots (any drink): 75 mg per shot. Their published nutrition PDF lists every drink.
Is caffeine in decaf really zero?+
No — decaf is ≥97% caffeine removed by regulation. 8 fl oz decaf drip: 2–7 mg. Five decaf coffees ≈ one regular. Meaningful for people with severe sensitivity.
Does caffeine help athletic performance?+
Yes — meta-analyses show 3–6 mg/kg body weight improves endurance ~2–4% and short-power output ~3%. Above 6 mg/kg the benefit plateaus and side effects rise. For an 80 kg athlete: 240–480 mg pre-event, timed 45–60 min prior.
Why does my tolerance vary day to day?+
Liver CYP1A2 activity fluctuates with sleep, alcohol intake, cruciferous vegetable consumption, and hormonal cycle. Same 200 mg feels wildly different — the variable is metabolism speed, not the dose.
Can I overdose on caffeine?+
Toxic dose ~150 mg/kg body weight — about 10 g for an 80 kg adult. Lethal dose ~200 mg/kg. Deaths on record are almost all from concentrated caffeine powder (a teaspoon = 5 g); dietary drinks essentially cannot reach it.
This article was written by The Turbo Unit Converter engineering desk (Applied nutrition metrology) and last reviewed on 2026-07-10 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.