For some, a morning coffee is only as good as the amount of caffeine per cup. Turns out you don’t need to go much further than your local convenience store to get the biggest bang for your buck. A lab test commissioned by BuzzFeed News found that 7-Eleven had the highest average amount of caffeine per medium cup of coffee. Compared with Starbucks, McDonald’s, and Dunkin’ Donuts, independent testing company Labdoor found an average of 280 milligrams of caffeine in 7-Eleven coffee, while the other brands’ average levels were significantly lower. However, this doesn’t necessarily mean you should give up your morning Grande Pike Place or Dunkin’ Dark if you’re craving more caffeine. While 7-Eleven’s high caffeine ranking was the result of the average among the 24 cups of coffee tested, one cup from each chain compared to another didn’t show as significant a difference.

“Statistically, they're all kind of overlapping,” Dan Mark, the research director for Labdoor told BuzzFeed News. “If you go to any one of these single chains and grab a medium cup of coffee you can expect around 250 milligrams of caffeine.” While Labdoor’s test found that Starbucks’s caffeine average per cup was 267 milligrams, McDonald’s McCafe’s was 227 milligrams, and Dunkin’ Donuts’s was 220 milligrams, Starbucks displayed the most consistent caffeine levels. 

Joseph DeRupo, a spokesperson for the National Coffee Association, told BuzzFeed News that a cup of coffee’s caffeine levels could be affected by tree variety, region, and the climate from which the beans were harvested. DeRupo also noted that caffeine level can have a lot to do with the brewing process, specifically with regards to how many spoonfuls of coffee go into each batch.

The BuzzFeed News test found that the caffeine concentration for each cup of Starbucks coffee—purchased at different stores in New York and San Francisco—was 17 milligrams per ounce, with only one cup clocking in at 16 milligrams per ounce. Dunkin' Donuts’s caffeine levels ranged from 16 to 20 milligrams of caffeine per ounce and a cup of McDonald’s coffee bounced from 10 to 17 milligrams, making it the largest variant in the findings. 7-Eleven’s deviation of 19 to 22 milligrams of caffeine per ounce may have pushed the convenience store to the front, but still there’s always something comforting about consistency. 

The answer is clear which coffee chain you should frequent if caffeine is the only reason for drinking. Taste, however, may be a whole other thing.