Will be close enough. I figured it out one time to be a tad over 14lbs when using our imperial gallon which is 10 lbs for water.Thanks you all. I am going with 12 pounds as the weight of 1 gallon of 2:1 sugar syrup.
I'm please to see that somebody else is puzzled by this, as the weight of this syrup will change as the bees remove water from it, prior to capping the result. The only important factor (imo) is the weight of the sugar itself.Why do you want to know the weight?