If you park at the airport - It's about a 20-30 minute journey from parking lot to the front door of the airport. If parking offsite it can even be longer.
Then going through TSA, even with pre-check, can be from 20-60 minutes. 20 minutes is about the minimum time, just due to how BIG the airport is. You can end up having to walk a mile door to gate. I can run a mile pretty fast, but that is generally frowned upon.
And if you need to somehow deal with an agent for checking bags or anything else? That can easily be another 30 minutes down the crapper.
My experience at ORD is that it's usually done in under 45 minutes, but takes longer often enough for me to budget ~90 minutes for security to be confident of making my flight.
