These things don't have great definitions, but here's how I've always personally viewed things:

• Ultra-wealthy (subset of the upper class): no need to work, net worth of $100M-$1B+ common. Your spouse runs a business that loses $100k/month for fun. Generational wealth, with no need for your kids to ever work and probably not their kids either.
• Upper class: no need to work, income primarily generated from investments, net worth of $5M-$50M, typically about $10M. The typical person here with a net worth of $10M generates a passive income of $400k/year forever, doing absolutely nothing.
• Upper middle class: corporate executives, top lawyers, surgeons. Incomes of $500k-$1M/year common. Typical net worth under $5M, either due to spending or just not enough time on the clock for investments to accumulate. Some could retire early, but choose not to because they couldn't maintain their lifestyle.
• Middle class: the bulk of the country, incomes ranging from $50k-$250k. Defined by living comfortably, but being totally reliant on an income with limited assets. Net worth under $1M typical. If net worth over $1M, then it's often tied up in home equity or otherwise illiquid. Limited to no ability to generate passive income.