First, IANAL.
Second, I'm going to assume you're talking about Pre-IPO shares here.
In most pre-IPO stock option grants your strike price (the fixed contracted value for which you can purchase the shares at) is usually close enough to zero that it is a rounding error in the overall computations.
Number of shares is completely insignificant, especially at this stage.
The two main things you want to find out (and any upstanding company would share with you) are:
1) What your shares represent as a percentage of the overall stock pool
2) What preferences the investors have in an equity event (sale, IPO, etc.).
Keep in mind too that these things are likely to change with every investment round. So while A-round shares are going to have a lower strike price (typically) and possibly a larger allocation than C-round shares, the C-round terms might be less volatile in regards to what they'll REALLY look like at the end.
Your options will probably come out to be somewhere between .01% and 2% of the overall stock pool. This is common for lower-level employees (and I'm only assuming you're lower-level and new to this based on your question, as most people have learned these deals the hard way by the time they've gotten to more advanced startup positions).
To be generous, let's assume your options are equal to 1% of the company. You would have been granted these options when the company might be deemed to have a value of 10 million dollars (note: you don't have anything that remotely resembles 1% of $10M in value. You have a right to purchase 1% of $10M).
Over time the company grows to be worth $500M. Your options grant you a fixed strike price at the $10M valuation, and now the company has grown in value by $490M. This seems like a good thing at first...
Your investors will almost always have what are referred to as preferred shares, and as their name implies they are going to get special treatment before your "common" shares. The investors might also have liquidation preferences. There is no "standard" here because literally everything can and does happen.
A not-atypical scenario though is that the investors have some terms that give them rights in a sale to get back their initial investment, plus some sort of interest, plus maybe a preferred payout of 2x-10x their investment.
Between the $10M and $500M valuation there was another $30M put into the company, making a $40M investment total. The investors have 3x liquidation rights, meaning that the first $120M of a sale is "theirs", then they have their preferred stock as well.
It's not uncommon to see a situation where a company sells for what seems like a HUGE number, but literally 70 or 90% of that sale amount goes to the investors/preferred share holders, and then the remainder goes to the common share holders in equal proportion.
So, what are your options worth? Who knows... Probably nothing at all unless the company is hugely successful and manages to establish itself as a true player in its industry. Anything less than total success is unlikely to yield an amount to common share holders that is worth anything significant overall.
My advice: options are nice. You're probably getting screwed, but shouldn't be working for the value of the options anyway. Work for a fair salary, consider the options a potential bonus if all the stars align. Anyone trying to tell you different, is lying to themselves or to you.
