How much caffeine is in Coca-Cola Diet Coke?

46 mg of caffeine in a 355 ml (12 fl oz) can, as recorded in the open dataset (TrackCaffeine dataset, accessed 2024-06-01).

Caffeine is a central nervous system stimulant.

The concentration in this can is 13 mg per 100 ml (TrackCaffeine dataset, accessed 2024-06-01), which is roughly half the caffeine contained in a 240 ml drip coffee that contains 96 mg per 240 ml (Mayo Clinic, accessed 2024-06-01); that comparison is why we list this drink as 0.5× a cup of drip coffee (TrackCaffeine dataset, accessed 2024-06-01). Every numerical claim on this page is tied to the open dataset entry for this specific product (see the dataset at /dataset/), and the 46 mg figure is the single value we use when calculating decay, daily-share, and simple comparisons (TrackCaffeine dataset, accessed 2024-06-01).

This dose is modest: it supplies 12% of the 400 mg/day guidance for healthy adults (U.S. FDA, accessed 2024-06-01), so one can treat a single 355 ml can as a low-contribution source of caffeine toward that limit (U.S. FDA, accessed 2024-06-01). The paragraphs below show what that 46 mg means through time, how it compares to similar sodas, and what can change the number in practice.

How long Coca-Cola Diet Coke stays in your system

We model caffeine elimination as a first-order process with a population-average half-life of 5.7 hours (TrackCaffeine decay model, population-average half-life 5.7 hours, 2026-08-02); the formula is remaining = dose × 0.5^(hours / 5.7). Using the can's dose of 46 mg (TrackCaffeine dataset, accessed 2024-06-01), that arithmetic gives: 46 × 0.5^(3/5.7) ≈ 46 × 0.695 ≈ 32 mg at 3 hours (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), 46 × 0.5^(6/5.7) ≈ 46 × 0.482 ≈ 22 mg at 6 hours (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), 46 × 0.5^(9/5.7) ≈ 46 × 0.333 ≈ 15 mg at 9 hours (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), and 46 × 0.5^(12/5.7) ≈ 46 × 0.232 ≈ 11 mg at 12 hours (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02).

As an example of what those numbers mean: if the can is finished at 15:00 (46 mg, TrackCaffeine dataset, accessed 2024-06-01), about 22 mg remain at 21:00 (6 hours later, TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), and about 11 mg remain at 03:00 the next day (12 hours later, TrackCaffeine decay model, 5.7 h half-life, 2026-08-02). Studies that measured sleep effects used larger doses—Drake et al. 2013 found that 400 mg consumed 6 hours before bedtime cost over an hour of sleep (Drake et al., 2013)—so this 46 mg can will not produce that magnitude of sleep loss, but the remaining tens of milligrams at bedtime can still fragment sleep in sensitive people (Drake et al., 2013).

The U.S. FDA's consumer guidance cites 400 mg/day as a reasonable upper limit for healthy adults (U.S. FDA, accessed 2024-06-01); this can supplies 12% of that daily guidance because 46 mg ÷ 400 mg = 0.115, or 12% (TrackCaffeine dataset, accessed 2024-06-01; U.S. FDA, accessed 2024-06-01). Under that guideline, eight full cans sum to 368 mg (8 × 46 mg = 368 mg, TrackCaffeine dataset, accessed 2024-06-01), which is under 400 mg, while nine cans reach 414 mg (9 × 46 mg = 414 mg, TrackCaffeine dataset, accessed 2024-06-01) and exceed the FDA guidance.

For sleep timing, experimental work suggests that large doses several hours before bed matter: Drake et al. 2013 reported that 400 mg given 6 hours before bedtime reduced total sleep time by over an hour (Drake et al., 2013); applying that window as a practical guideline implies avoiding caffeine within about 6 hours of bedtime, which for a 23:00 bedtime would mean finishing caffeine by roughly 17:00 (Drake et al., 2013). Given the decay arithmetic for this 46 mg dose (46 mg → ~22 mg after 6 hours, TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), a single can consumed at 17:00 would leave about 22 mg at 23:00 (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02), and that remaining amount can marginally delay sleep onset in sensitive individuals (Drake et al., 2013).

Special populations should use stricter thresholds: EFSA recommends a 200 mg/day limit in pregnancy (EFSA Scientific Opinion on the Safety of Caffeine, 2015), so one 46 mg can is 23% of that 200 mg pregnancy guidance (46 mg ÷ 200 mg = 0.23, EFSA, 2015). Adolescents and people with known sensitivity should consult the tailored guidance in our safe daily limit by body weight tool and consider keeping daily caffeine to a small fraction of adult limits (TrackCaffeine dataset, accessed 2024-06-01).

If precise bedtime planning is required, try the half-life calculator at /tools/caffeine-calculator/ or the last-cup planner at /tools/last-cup-before-bed/ which use the same 5.7 h half-life baseline as this page (TrackCaffeine decay model, 5.7 h half-life, 2026-08-02).

This Diet Coke entry (46 mg per 355 ml, TrackCaffeine dataset, accessed 2024-06-01) sits below many energy drinks and above several colas: Mountain Dew at 54 mg per 355 ml is higher (TrackCaffeine dataset, accessed 2024-06-01), Dr Pepper at 42 mg per 355 ml is slightly lower (TrackCaffeine dataset, accessed 2024-06-01), Pepsi at 38 mg per 355 ml is lower (TrackCaffeine dataset, accessed 2024-06-01), and Club-Mate at 66 mg per 330 ml is substantially higher (TrackCaffeine dataset, accessed 2024-06-01).

Compared to coffee, a 240 ml drip coffee at 96 mg per 240 ml contains about twice the caffeine of this 355 ml can (96 mg per 240 ml, Mayo Clinic, accessed 2024-06-01), which is why the dataset lists this soda as roughly 0.5× a cup of drip coffee (TrackCaffeine dataset, accessed 2024-06-01). For side-by-side visual comparisons use the interactive tool at /tools/caffeine-comparison/ (TrackCaffeine dataset, accessed 2024-06-01).

What changes the number for Coca-Cola Diet Coke

The 46 mg value is an aggregate figure for the named product and serving; several real-world factors can move that number and are why the published value is an estimate (TrackCaffeine dataset, accessed 2024-06-01). Size is the simplest: a 330 ml variant of the brand is recorded at 32 mg (TrackCaffeine dataset, accessed 2024-06-01) while a 355 ml can is 46 mg in this entry (TrackCaffeine dataset, accessed 2024-06-01); different can sizes therefore change the total proportionally at the measured concentration.

Formula differences between variants also change caffeine content: for closely branded sodas we record Coca-Cola (355 ml) at 34 mg and Coca-Cola Coke Zero (355 ml) at 34 mg in the dataset (TrackCaffeine dataset, accessed 2024-06-01), while Diet Coke in this entry is 46 mg for 355 ml (TrackCaffeine dataset, accessed 2024-06-01); that spread shows that a single brand name can contain multiple formulations with different caffeine amounts (TrackCaffeine dataset, accessed 2024-06-01).

Other causes of variation include manufacturing tolerances, regional formulations, and lab-to-lab measurement differences: bottled and canned sodas can show batch-to-batch variance of several milligrams per serving in public lab data (USDA FoodData Central, accessed 2024-06-01). If a consumer needs a precise intake log, choose the exact SKU page (for example, see Coca-Cola (330 ml) and Coca-Cola (355 ml)) and consider measuring with multiple entries from our open dataset to capture range.

• Decaffeinated or caffeine-free alternatives exist and remove nearly all caffeine: see the guide Caffeine-Free Coca-Cola: Complete Drink Options for options and measured values (TrackCaffeine dataset, accessed 2024-06-01).

Where this figure comes from

The 46 mg value shown here is taken from the TrackCaffeine open dataset entry for this named product (TrackCaffeine dataset, accessed 2024-06-01), which compiles manufacturer declarations and laboratory analyses and records the serving-size and concentration as 13 mg per 100 ml (TrackCaffeine dataset, accessed 2024-06-01). Primary public chemical-composition sources such as USDA FoodData Central list measured values that sometimes differ by a few milligrams per serving because of sampling date, region, and analytical method (USDA FoodData Central, accessed 2024-06-01).

We will update this page if a manufacturer revision or a new authoritative lab measurement appears in the dataset (TrackCaffeine dataset, accessed 2024-06-01); for transparency the underlying entries and their timestamps are available at /dataset/, and the USDA FoodData Central entry is a primary reference for lab values (USDA FoodData Central, accessed 2024-06-01).

Bottom line

This 355 ml can contains 46 mg of caffeine (13 mg per 100 ml) as recorded in the open dataset (TrackCaffeine dataset, accessed 2024-06-01). That dose is about 0.5× a 240 ml drip coffee at 96 mg per 240 ml (Mayo Clinic, accessed 2024-06-01) and supplies 12% of the 400 mg/day guidance for healthy adults (U.S. FDA, accessed 2024-06-01); after 6 hours about 22 mg remain under a 5.7 h half-life model (TrackCaffeine decay model, population-average half-life 5.7 hours, 2026-08-02).