And it depends on what type of leg press machine you are using. I have seen dozens of different varieties and they all "feel" different and alow you to use a different amount of weight. My gym has a couple of selectorized machines, one I can barely do 140 pounds on, another I can do the entire stack of 500 pounds and a couple of plate loaded ones I can do over 1,000 pounds on. It also depends on what ROM you are using. I saw a skinny little guy at the gym the other day and he put 1500 pounds on one of the plate loaded leg press machines, but never released the catches so he was lifting from the catches to lock out, only about a 2" ROM! I always try to get the maximum ROM I can on any leg press machine and when I squat.
An interesting anechdote for what it is worth. Many years ago I also went to a gym where there wa no squat rack. They had a nautilus brand leg press machine. I used that heavily for a couple of years. Then they remodeled and added a squat rack. So I decide to try squating again. Started with 145, 12 reps no problem. When up to 195, again 12 reps no problem. Loaded up 225. At the bottom of the first rep something in my back popped. It hurt a little so I hit the showers. The next morning the back spasms started and I could not get out of bed for 3 days! Fortunately I had only strained a muscle and there was no permanant damage. The moral of the story is, even though your quads might be strong enough to squat more, your supporting muscles may NOT be ready to assist, so go slow when you start squating.