I weigh feed everytime I feed. The scoop I use is a smaller one. I would say I could get 2 cup of feed in it and that would weigh 1/2 a pound. I give my guys two scoops in am and two scoops in pm. One pound every feeding. I may be over feeding, the sweet 12 feed weighs real close to the complete pellet feed. I hope this helps.
Feeds don't all weigh the same and not all coffee cans are the same size. So it's important for you to weight your feed yourself.
You can get a scale at Walmart for very little that will allow you to take the container you are going to be scooping with and put it on the scale and zero it out. This will mean that when you scoop feed and put it on the scale it will only be weighing the feed.
If you want someone else to double check you, you will need to give the name of the feed you are using and exactly what coffee can you are using (brand/size).
Get a scale for sure. I just started giving my guy "lunch" on my own (to help him gain) and I was shocked at how much 3 POUNDS of grain is. I use a little kitchen scale, put my feed bowl on the scale and then adjust it to zero (or any pound increment) and add feed until it goes up 3 pounds. It takes alot of feed to equal the 3 pounds. You definitely need a scale for an accurate weight measurement. Good luck!