It really isn't.
That would be anything over 0.5xg.
A penalty is 0.7xg and is never referred to as an open goal.
Mainly because the keeper has a chance of saving it.
But an open goal is generally an opportunity that any shot on target will score.
As I mentioned earlier, our entire xg was...
Was it an open goal?
Certainly a free header, which he should have hit the target from.
But to my mind, an open goal has to register at least 0.7 in xg and we only mustered 0.6 from the whole game.