A little lighter than plain milk chocolate
USDA measures M&M’s Milk Chocolate at 14 mg of caffeine per 100 g, which comes to about 7 mg in a standard 1.69 oz (48 g) pack. That’s a bit below USDA’s generic figure for milk chocolate (20 mg per 100 g), likely because the candy shell and any fillings dilute the chocolate content per gram compared to a solid bar.
Negligible next to coffee or dark chocolate
A whole pack’s 7 mg is a fraction of an 8 oz cup of drip coffee at USDA’s reference strength (95 mg), and far below an ounce of dark chocolate (about 23 mg), which has much more cocoa solids per gram.
Other M&M’s varieties differ
This figure is specific to the Milk Chocolate variety. Peanut, pretzel, or dark chocolate M&M’s have different ratios of chocolate to filling, which changes the caffeine per pack even at the same total weight; a filled candy generally carries less caffeine per gram than a solid chocolate piece, since the filling itself contributes none.
Where it fits in a day
At 7 mg, a pack is negligible against the 400 mg daily figure the FDA cites for healthy adults; dozens of packs would be needed to approach it. It matters most for children, whose smaller daily allowances make even a low-caffeine snack a slightly larger share of the day, and it’s a reminder that the FDA notes naturally occurring caffeine, like the kind in chocolate, doesn’t have to be listed separately on a nutrition label.