Ideally, you should raise as much money as you need to reach profitability, so that you’ll never have to raise money again. If you succeed in this, not only will you find it easier to raise money in the future, you’ll be able to survive without new funding if the funding environment gets tight. That said, certain kinds of startups will need a follow-on round, such as those building hardware. Their goal should be to raise as much money as needed to get to their next “fundable” milestone, which will usually be 12 to 18 months later.
In choosing how much to raise you are trading off several variables, including how much progress that amount of money will purchase, credibility with investors, and dilution. If you can manage to give up as little as 10% of your company in your seed round, that is wonderful, but most rounds will require up to 20% dilution and you should try to avoid more than 25%. In any event, the amount you are asking for must be tied to a believable plan. That plan will buy you the credibility necessary to persuade investors that their money will have a chance to grow. It is usually a good idea to create multiple plans assuming different amounts raised and to carefully articulate your belief that the company will be successful whether you raise the full or some lesser amount. The difference will be how fast you can grow.
One way to look at the optimal amount to raise in your first round is to decide how many months of operation you want to fund. A rule of thumb is that an engineer (the most common early employee for Silicon Valley startups) costs all-in about $15k per month. So, if you would like to be funded for 18 months of operations with an average of five engineers, then you will need about 15k x 5 x 18 = $1.35mm. What if you are planning to hire for other positions as well? Don’t worry about it! This is just an estimate and will be accurate enough for whatever mix you hire. And here you have a great answer to the question: “How much are you raising?” Simply answer that you are raising for N months (usually 12-18) and will thus need $X, where X will usually be between $500k and $1.5 million. As noted above, you should give multiple versions of N and a range for X, giving different possible growth scenarios based on how much you successfully raise.
There is enormous variation in the amount of money raised by companies. Here we are concerned with early raises, which usually range from a few hundreds of thousands of dollars up to two million dollars. Most first rounds seem to cluster around six hundred thousand dollars, but largely thanks to increased interest from investors in seed, these rounds have been increasing in size over the last several years.