Celsius vs C4 Energy: caffeine compared
Celsius and C4 Energy carry the same caffeine per serving: 200 mg each. Per fluid ounce, Celsius is the stronger drink: 16.7 mg/oz versus 12.5 mg/oz.
| Celsius | C4 Energy | |
|---|---|---|
| Serving | 12 oz | 16 oz |
| Caffeine per serving | 200 mg | 200 mg |
| Per fl oz | 16.7 mg | 12.5 mg |
| Share of 400 mg/day | 50% | 50% |
| Servings to reach 400 mg | 2.0 | 2.0 |
| Hours until under 50 mg | 10.0 h | 10.0 h |
| Last one for an 11 PM bedtime · standard (50 mg) | 1:00 PM | 1:00 PM |
| Last one for an 11 PM bedtime · sensitive (25 mg) | 8:00 AM | 8:00 AM |
| Share of the 200 mg pregnancy limit | 100% | 100% |
One serving of each, over 16 hours
Common questions
Which has more caffeine, Celsius or C4 Energy?
Neither: both have about 200 mg per serving.
Which is stronger per ounce, Celsius or C4 Energy?
Celsius: about 16.7 mg per fl oz versus 12.5 mg for C4 Energy. Serving size decides the total you actually drink.
When should I stop drinking Celsius or C4 Energy before bed?
For an 11 PM bedtime with a 50 mg limit and a 5-hour half-life: last Celsius by 1:00 PM, last C4 Energy by 1:00 PM. Half-life varies from about 1.5 to 9.5 hours between people.
Method
Caffeine per labeled serving, from the same drink table every calculator here uses (FDA/USDA reference amounts and manufacturer labels; see caffeine content of every drink). Brewed drinks vary batch to batch, so read these as typical values. Decay uses a 5-hour average half-life with a 45-minute absorption ramp; cutoff = bedtime − 5 h × log₂(dose ÷ limit). Percentages use the FDA's 400 mg/day figure for healthy adults and the 200 mg/day limit ACOG gives for pregnancy.
Source — Celsius: CSPI caffeine chart (Celsius, 12 oz), checked 2026-10-13.
Source — C4 Energy: CSPI caffeine chart (C4 Performance Energy, 16 oz), checked 2026-10-13.