There's no standard amount of caffeine in each cup of coffee—even within the same brand. Starbucks gives an approximation of 20 milligrams per ounce. One 16-ounce cup of Starbucks puts you at about 320 milligrams of caffeine. One 16-ounce cup of Starbucks is for many Americans a good daily dose of caffeine. One researcher found that a 16-ounce cup had 560 milligrams of caffeine.
http://www.motherjones.com/environment/2014/03/caffeine-murray-carpenter-energy-drink-keurig-cup-coffee/
The Facts about Caffeine in K-Cups. The standard cup of coffee has 120 mg of caffeine in an 8 fl oz cup. However, an 8 oz cup of coffee from a standard 2 oz K-Cup contains between 100-140 mg of caffeine. Most K-Cups consist of 2 tablespoons of ground coffee which equals 2 ounces of coffee.
http://www.coffeeforless.com/blog/over-a-single-cup-coffee/whats-the-actual-amount-of-caffeine-in-k-cups/
1 The hotter the water used in brewing, the higher the caffeine. Although you should not brew above 212 degrees.  Obviously, the amount of grounds used will change the caffeine content of the resulting cup of coffee. Extra bold Keurig Kcups contain twenty percent more coffee translating to a more caffeinated cup of joe.
http://blog.crosscountrycafe.com/blog/bid/336041/How-Much-Caffeine-is-in-a-Keurig-Kcup
Coffees Serving Size Caffeine (mg) Dunkin' Donuts Coffee with Turbo Shot large, 20 fl. oz. 436. Starbucks Coffee venti, 20 fl. oz. 415. Starbucks Coffee grande, 16 fl. oz. 330.
http://deploymentpsych.org/system/files/member_resource/Caffeine%20content%20list.pdf
Just how much caffeine is in Keurig K-cup coffee? This is a commonly asked question that unfortunately does not have a precise answer Kcup coffee contains between 75-125mg of caffeine per 6 fluid ounces. I know, I know, that really is not very helpful.
http://blog.crosscountrycafe.com/blog/bid/336041/How-Much-Caffeine-is-in-a-Keurig-Kcup
The actual caffeine content of the same coffee drink can vary from day to day — even at the same coffee shop — because of various factors, such as roasting and grinding as well as brewing time. The caffeine content of tea also is affected by how long it's brewed.
http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/caffeine/art-20049372
But, there are so many variables that determine the amount of caffeine in a cup of coffee, it is near impossible to estimate an exact amount. Caffeine varies by roasting type. Contrary to popular belief light roast coffee contains more caffeine than dark roast.
http://blog.crosscountrycafe.com/blog/bid/336041/How-Much-Caffeine-is-in-a-Keurig-Kcup
Consuming the equivalent amount in K-Cups adds up to $400 a year (8 lbs*$50, the average price per pound of K-Cup coffee), over four times as much. Let's be real — most of us are probably drinking more coffee than that. The Huffington Post recently reported that the average American consumes 2.1 cups per day, putting our numbers at $190 per year for the Coffee Potters and $800 for the K-Cuppers.
http://www.businessinsider.com/keurig-cups-are-expensive-2015-3
But do you know the caffeine content of your favorite drink? You may want to take a look at just how much caffeine you get in a typical day, especially if you're bothered by headaches, restlessness or anxiety. If your caffeine habit totals more than 500 milligrams (mg) a day, you may want to consider cutting back. With the growing popularity of energy drinks, many parents have become concerned about how much caffeine their kids are getting. The American Academy of Pediatrics recommends that adolescents get no more than 100 mg of caffeine a day.
http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/caffeine/art-20049372
But, there are so many variables that determine the amount of caffeine in a cup of coffee, it is near impossible to estimate an exact amount. 1  Caffeine varies by roasting type. 2  Different types of beans will produce more caffeine than others.  The finer that a coffee is ground the more caffeine it will contain.
http://blog.crosscountrycafe.com/blog/bid/336041/How-Much-Caffeine-is-in-a-Keurig-Kcup
average caffeine of k cups
On an average two ounces of the K Cup contains 100 to 140 milligrams of caffeine. A 2 ounce of K-cup contains between 100 and 140 milligrams of caffeine.