The caffeine in a cup of coffee depends on quite a few factors: the bean, the roast, the brewing method, the size of the beverage and how quickly it is consumed. Although this last factor is not an actual measure of caffeine levels in a drink, it does alter how that caffeine affects our bodies.
A CLOSER LOOK
The coffee bean is the primary source of coffee's caffeine. Caffeine content varies according to a variety of influences like the local environment where the coffee plant is grown, length of the growing season, time of harvest, and the species of plant. Each bean on a specific bush can even vary slightly in caffeine level!
There are two main species of coffee plants used to produce coffee - Coffee Arabica and Coffee Canephora (Robusta). Coffee Arabica constitutes 75% of the coffee beans grown worldwide for the commercial coffee industry. It is mainly grown in Central and South America and contains, on average, 1.1% caffeine. Coffee Robusta is the second most popular bean to grow. It is often used as a filler for Arabica blends. It is mainly grown in Indonesia and Africa and contains, on average, 2.2% caffeine. Other varietals and their caffeine content include Tanzania peaberry with 1.42%, Yemen mocha with 1.01%, Guatemalan with 1.20%, Kona with 1.32% and Ethiopian harrar with 1.13%.
The simple answer is not so simple.
How a roast affects the caffeine in your coffee really depends on how you decide to measure the amount of roasted coffee.
- Caffeine Per Bean - A light roast bean compared to a dark roast bean has virtually the same amount of caffeine. Contrary to popular belief, caffeine does not burn off during the roasting process. To change the caffeine content of an individual bean, you would need to roast it at temperatures above 600°F. Since roasting temperatures rarely exceed 470°F, a bean's caffeine level remains relatively the same across all roasting levels light to dark.
- Caffeine By Weight - When green coffee beans are being roasted, they lose water weight. In a dark roast process, the beans roast longer and lose more water weight. In order to compare 2 ounces of a dark roast with 2 ounces of a light roast, you would need more dark roast beans. To rephrase, it takes more dark beans than light beans to compose two ounces. Therefore, when 2 ounces are comparatively brewed to make a cup of coffee, the larger amount of dark beans needed will result in a slightly higher caffeine amount per cup. Coffeehouses (and often people at home) brew coffee according to weight. Therefore, a dark roast at a coffeeshop will most likely be more caffeinated than a lighter roast.
- Caffeine By Volume - If you measure caffeine by volume of beans used to brew a cup, there is more caffeine in a light roast. When a green coffee bean is roasted, it physically expands. A light roast bean will be smaller than a dark roast bean. So a scoop of light beans will have more smaller beans that the same scoop of dark beans. The larger amount of small light beans translates to a more caffeinated cup of coffee since more beans are used to brew it. It is common at restaurants that coffee is measured and brewed by volume. In that scenario, comparably with the same volumes, the light roast cup of coffee will have slightly more caffeine.
The Brewing Method
Once again, we have a few fun factors that come into play.
- Amount of Ground Coffee Used - No matter what the brewing process, if you use more coffee grounds, you will get more caffeine into your cup of coffee.
- Saturation - Only a 100% saturation of the grounds will allow all of the caffeine possible to be extracted.
- Brew Temperature - The hotter the water used, the more caffeine. The lower the temperature water used, the less caffeine. Proper coffee extraction happens between 195-205 degrees. Most drip brewers only get up to 190 degrees. Espresso machines reach near boiling, 212 degrees. French press lets you have control over the temperature of the water you pour over the grounds. It is recommended to not go above 205 degrees. Take note...water boils at 212 degrees.
- Brew Time - Usually the longer the brew time (amount of time the beans are in contact with the water), the more caffeine there will be. Drip brew goes through the coffee for three minutes. A shot of espresso is pulled in 20-30 seconds. Drip brew has more caffeine than an espresso when comparing ounce per ounce! However, French Press has a recommended steep time of 4 minutes but it has less caffeine than drip coffee. How could that be? Please read on...
- Grind Level - The coarser the grind, the less caffeine will be extracted. French press coffee is more coarse than drip coffee. Drip coffee uses a medium grind. While espresso is finely ground.
Beverage Size & Consumption
When comparing caffeine levels across a variety of coffee bean beverages, you need to compare them ounce for ounce and then drink for drink. Ounce for ounce, espresso has more caffeine than drip coffee. Espresso coming in at 40 mg per ounce, and drip coffee at 10 mg. However, an espresso is done as a shot or double shot (1 or 2 ounces) while drip coffee is consumed, on average, in 12 oz mugs. A 2 oz double espresso shot has 80 milligrams of caffeine compared to a drip coffee's mug of 12 oz having 120 milligrams of caffeine.
But of course, there is a catch. How quickly you consume the caffeinated beverage contributes to how you experience the affects of the caffeine in the beverage. An espresso shot is consumed quickly and hits the nervous system hard and fast. Caffeine is better assimilated in more concentrated doses. In comparison, a mug of coffee is often sipped over a longer period of time and the caffeine is not assimilated by the body as well.
How Does Coffee Stack Up?
A rough comparative chart by the USFDA can be seen below. It does not account for all of the variables described above.
|Robusta Coffee (drip brewed)||
140 - 200 mg caffeine per 6 ounce average cup
|Arabic Coffee (drip brewed)||
75 - 130 mg average 6 ounce cup
|Arabica/Excelsa Blend Coffee (drip brewed)||
40 - 60 mg average 6 ounce cup
|Espresso (typical serving)||
30 - 50 mg average 1 ounce shot
40 - 100 mg average 6 ounce cup
|97% Decaf Coffee||
3 - 6 mg caffeine per 6-7 ounce average cup
|99.92% Euro Decaf Standard Coffee||
8 - 16 mg caffeine per 6-7 ounce average cup*
10 - 15 mg caffeine per 6-7 ounce cup
|Dark Chocolate Candy Bar||
50 - 100 mg caffeine per 6 ounce bar
|Milk Chocolate Candy Bar||
30 - 50 mg caffeine per 6 ounce bar
|Coke, Pepsi, Mountain Dew||
20 - 26 mg caffeine per 6-7 ounce drink
|Green Tea (brewed)||12 - 30 mg per 6-7 ounce average cup|
|Black Tea (brewed)||40 - 60 mg per 6-7 ounce average cup|
* - 99.2% Euro standard decaf actually has more caffeine than 97% FDA standard decaf when measured on equal terms.
Caffeine, like so many other coffee topics (and topics in general in life), is not so straight forward. However, we have tried to simplified the most important information for you and hope that armed with this knowledge you do what works for your body and your baby.