I measure it in a 5 gallon bucket (currently 5 scoops, about 12#, maybe 50-60% of a 5 gal bucket in height). I walk back towards the coop, open the spigot on my rainwater collection system, start filling. While it fills, I stir with a big stick till I have oatmeal. Take a few minutes, and probably 2-3?? gallons of water.
Then finish walking into the run, and start pouring it out, sort of sludgy, into 5" plastic gutters I use as feed troughs. Hang out about 10 min and watch the flock. They should take about that long to finish the majortiy of it, and a good number wander off.
If they almost all stop before then, and walk off I cut the feed ration by a half scoop. If they finish it all bu 7-8 minutes and start mobbing my feet, I add a half scoop.