> I figure I need to work out what the company could be worth

That's how I approached things when I worked at a few startups in the past. If I were to work at a startup again, that's not what I would do. You want to look at the company's worth now. You are investing in the company. You are investing your time, you are investing the opportunity cost of making more elsewhere, and you are forgoing any dividends you'd get from earning and saving elsewhere. For people early in their careers, those opportunity costs aren't that big, but if you are managing a team, chances are those opportunity costs can be quite big.

When VCs look at how much to invest in a company, they are investing in what the company's worth now. For pre-revenue start-ups, they'll look at potential some (the founding team, the size of the market, stuff like that), but a company that is all potential today will get a low valuation. For companies that have revenue, they might look at what a certain amount of money might due to fuel future growth. But VCs aren't charities. They don't evaluate their stakes today based on what a company might be worth someday in the future. Neither should we.

The other problem with figuring out what the company could be worth is: at what point in time? Companies are waiting longer to go public [1]. Are you willing to wait for an IPO? Or will the company have some non-public way of getting liquidity from shares? Depending on those details, the shares you vest a year from now might not only take several years to be worth something meaningful, but you might have to wait several more years to actually sell them.

> and then consider what a percentage of options would provide.

I recommend you read the book Venture Deals by Brad Feld. When I first joined a start-up, I thought, "Ah, I got X% of the equity." Feld talks through how it doesn't really work that way. As an employee, you have a chunk of the employee pool stock options, but what that means depends on a whole lot of variables (which he describes better than I could). It can also change over time.

Finally, I'd offer a few other pieces of related advice:

1. The best reason to join a startup is because they are solving a problem that you feel like you have to work on. I wouldn't do it for the money, because in most cases, start-ups aren't successful.

2. Really, all most of us aspire to in our careers is to be able to say "I very much enjoy my current job, they are very good at rewarding me and give a good level of autonomy to run my engineering team that I acquired and grew myself." Don't feel the need to stay complacent, but also don't take that for granted.

3. At least for me, working for a large, publicly-traded tech company has financially paid off as well as the "What-if?" scenario of the start-ups I worked for, with the difference that start-ups don't always pan out. It's not apples-to-apples comparing working at a large company vs. the big payday, since the big payday is usually at least 5, and often more like 10 years out. So when figuring out what the exit might be, look at how much stock you could be forfeiting at your current company (or at a different publicly traded company) over the course of 5-10 years (and how much that stock might grow in that time period).

Good luck!

[1] https://equityzen.com/knowledge-center/newsletter/the-ipo-cr...

[2] https://www.amazon.com/Venture-Deals-Smarter-Lawyer-Capitali...