Eliminate the guesswork. Real information is available! According to this site
, a 322g serving of maple syrup contains 192g of sugar. In ounces (by weight
) that's an 11.35 oz serving with 6.77 0z of sugar. That means that every ounce of syrup has 0.596 oz of sugar in it. I recall reading somewhere that the sugar in maple syrup is almost entirely sucrose. I'm too lazy to look it up right now, but someone can check me on that.
For a 3 gallon batch of beer, 2 oz of sucrose will get you a carbonation level of 2.4 volumes, usually considered the "normal" or "average" level of carbonation. Divide 2 oz by 0.596 and you get 3.35 oz of syrup.