How much caffeine is in 30 grams of ground coffee, according to Reddit?

January 10, 2026 •

4 min read

According to discussions on Reddit, a common estimate suggests that 30 grams of Arabica ground coffee contains roughly 300 mg of caffeine, though this is a general guideline. The actual amount can fluctuate significantly based on bean type, roast level, and brewing method, making it a surprisingly complex question for enthusiasts and casual drinkers alike.

Quick Summary

This article explores the varying caffeine content in 30 grams of ground coffee, referencing insights from Reddit's coffee community. It explains how factors like bean species, roast level, and brewing method influence the final caffeine yield. A comparison of average caffeine extraction across popular brewing techniques is provided to offer a comprehensive answer.

Key Points

Start with the Source: Robusta beans can have almost double the caffeine of Arabica beans, so the type of bean used is the most crucial factor.
Roast Level is Less Important: For a fixed weight of 30g, the roast level has a negligible effect on total caffeine content; the stronger taste of dark roasts is often misleading.
Brewing Method Matters: Longer extraction times, like those used in cold brew or French press, tend to yield more total caffeine from the grounds than faster methods like espresso.
Reddit's Rule of Thumb: A popular estimate mentioned on Reddit suggests about 10mg of caffeine per gram of ground coffee, putting 30g at roughly 300mg, though this is a simplification.
Measure by Weight: For consistent caffeine dosing, always measure coffee grounds by weight rather than by volume (scoops), as roast levels affect bean density.
Consider Extraction Efficiency: Not all caffeine in the grounds makes it into your cup; brewing variables determine the extraction efficiency.

The Caffeine Conundrum: Diving Deeper than a Simple Number

While a simple number might seem sufficient, answering "How much caffeine is in 30 grams of ground coffee?" is far from straightforward. The Reddit coffee community, known for its deep dives into brewing science, highlights numerous variables that influence the final caffeine content. The prevailing consensus is a ball-park figure, but the true answer lies in understanding the complex interaction of bean origin, roast profile, and brewing technique.

Bean Type: Arabica vs. Robusta

The species of coffee bean is the most significant factor determining baseline caffeine content. Robusta beans, known for their bold and often bitter flavor profile, contain a substantially higher concentration of caffeine than the smoother, more complex Arabica beans.

Arabica: Typically contains about 1.2% caffeine by weight. So, 30 grams of pure Arabica beans would hold approximately 360 mg of caffeine before brewing.
Robusta: Features a much higher caffeine content, averaging around 2.2% by weight. The same 30 grams of Robusta could contain as much as 660 mg of caffeine.
Blends: Many commercial coffees are blends of both Arabica and Robusta, meaning their total caffeine content falls somewhere between these two extremes. Without knowing the exact ratio, a precise number is impossible.

The Misconception of Roasting and Caffeine

A common myth is that darker roasts have more caffeine because they taste stronger. In reality, the opposite is slightly true, but the difference is minimal when measured by weight. The roasting process does not destroy caffeine, which is a heat-stable compound. However, beans lose mass as they roast, meaning a scoop of dark roast beans (measured by volume) will be lighter and contain fewer total beans than a scoop of light roast. When measured consistently by weight (e.g., 30 grams), the caffeine difference is negligible. As one user on Reddit pointed out, the caffeine content is determined more by the bean variety than the roast level.

Brewing Method and Extraction

The brewing process is where a significant amount of variability is introduced. How long the ground coffee is in contact with water, the water temperature, and the fineness of the grind all impact how much of the total caffeine is extracted. For example, espresso, with its quick, high-pressure extraction, yields a highly concentrated brew but doesn't necessarily extract all the caffeine from the grounds. A longer immersion method like a French press can extract more overall caffeine from the same amount of grounds.

A Comparison of Brewing Methods


Brewing Method	Estimated Caffeine Extracted (mg) from 30g of Arabica	Notes
Pour Over	240-270 mg	Moderate extraction time and temperature, yielding a clean cup.
French Press	270-300 mg	Full immersion allows for maximum extraction, including more oils and potentially more caffeine.
Espresso	180-210 mg	While concentrated, the fast extraction time and small water volume can lead to lower total caffeine yield compared to immersion.
Cold Brew	280-320 mg	Long steeping time (12-24 hours) with a high coffee-to-water ratio draws out a high amount of caffeine, despite using cold water.

A Reddit Thread's Calculation

A highly-cited post on Reddit from the r/Coffee subreddit provides a pragmatic estimate, based on the assumption of 10 mg of caffeine per gram of ground Arabica coffee. Using this popular rule-of-thumb, 30 grams would equate to approximately 300 mg of caffeine in the brewed pot, assuming near-total extraction. While this is a useful starting point, it's crucial to remember this is an average, and individual brews will vary.

The Final Reality: It's Complicated

Ultimately, a single number for how much caffeine is in 30 grams of ground coffee is elusive. Reddit users highlight the numerous variables at play, from the inherent genetics of the bean to the precise brewing parameters. An Arabica-based coffee will likely yield a result in the 250-300mg range for a typical home brew, but using Robusta beans or a long, aggressive extraction could push that number significantly higher. For those tracking their intake, knowing the coffee type and consistently measuring by weight are the best ways to get a reliable estimate. For a more scientific perspective on the chemistry of coffee extraction, sources like research papers on platforms such as ResearchGate provide detailed insights into the process.

Conclusion: The Range is the Answer

The conversation on Reddit confirms that the caffeine content of 30 grams of ground coffee is not a fixed value but a range influenced by several factors. While a 300mg estimate for a standard Arabica brew is a good reference, the actual dosage depends heavily on the bean type (Arabica vs. Robusta) and your specific brewing method. For the coffee aficionado, these variations are part of the fun, but for someone monitoring their caffeine intake, they are critical considerations. Always remember that the extraction efficiency and serving size have a bigger impact on your final cup's kick than the roast level alone.

Frequently Asked Questions

When measured by weight (30 grams), the difference in caffeine content between a light and dark roast is minimal and often negligible. The misconception that dark roasts have less caffeine comes from measuring by volume, as dark roast beans are less dense.

Differences in reported caffeine levels can be attributed to the type of beans (Arabica vs. Robusta), the efficiency of their brewing method, and the degree of extraction. Robusta beans and longer brew times lead to higher caffeine yields.

The type of bean is the most significant factor. Robusta beans are naturally higher in caffeine, containing about 2.2% by weight, compared to Arabica beans at about 1.2% by weight. A 30g dose of Robusta would contain significantly more caffeine than a 30g dose of Arabica.

The 10mg per gram rule is a useful starting estimate for Arabica coffee, as widely discussed on Reddit. However, it is an average and can vary depending on the bean and brewing method. Use it as a general guideline rather than an exact measurement.

For 30 grams of Arabica coffee, you can typically expect to extract somewhere between 250 and 320mg of caffeine. The specific amount depends heavily on your brewing method, with cold brew often extracting the most and a quick espresso yielding a bit less.

Yes, grind size directly affects extraction. Finer grinds, like those for espresso, have more surface area, leading to quicker and more efficient extraction. Coarser grinds, like for French press, require longer brew times to achieve a similar level of extraction.

Generally, hotter water extracts caffeine more efficiently and quickly than colder water. This is why cold brew relies on a long steeping time to compensate for the lack of heat and still achieve a high caffeine yield.