We won't keep you from your coffee.
The advice above is very good, and I don't differ with any of it. The "thumb rule" for a typical adult chicken (not that any of us have a theoretically average bird in all respects) is about 100g or 1/4# ration of a complete feed per day. Offering it free feed, from mulltiple feeders, then trusting the birds to adjust consumption based on what they are able to tractor in addition is a very reasonable management practice, pursued successfully by many.
I'll add a bit of experience here, which you should take as anecdote, NOT data.
My birds free range acres (flock in Signature, below). In some ways, its superior to tractoring, as they are less prone to dietary imbalance that way - they can select from everything growing in their range, not just whatever happens to be growing in the 100-200 square feet under the tractor. During the height of my growing season (and I'm very fortunate - lousy soil, but one of the most forgiving climates in the US - 8a, with regular rainfall), I can save about 35% off my anticipated feed budget.
I still check my birds for nutritional imbalance every ten days to two weeks, internally and externally,
as part of regular cullings. The down side of free ranging is that I can't control what they are eating, either. There are times of year when they tend to put on a bit of extra fat - too many seeds coming ripe at the same time - and I continue to adjust my pasture in an effort to produce a better blend for them. It will be a lifelong effort.
