1/3 of your net income.
Let's say you make 150k base salary in the state of California. After taxes that's around 92k as your net income excluding yearly profit sharing, bonuses, and stock options. 1/3 of that is around $2500 a month. So $2500 should be what you spend on rent each month.
The 1/3 amount is just a common amount in personal finance. However, you can spend more since you still have 5,000 left over. That's more leftover than let's say... Someone making 80k a year. There's also your yearly bonuses which can also be a lot, possibly half of your base income or more.At least that's how it is in San Francisco.