Your valuation is driven by your exit value and money multiple.
If you raise a Series Seed or Series A you can use the following logic to calculate your exit value (all numbers are at the time of exit):
What is your startup’s market size? Assume $50m.
What is your market share? Assume 20%.
A $50m market and a 20% market share results in $10m revenue per year.
What multiple is a buyer willing to pay for your startup? You can look this up at dealroom.co. Assume a 3.0x revenue multiple.
A $10m revenue and a 3.0x revenue multiple results in a $30.0m exit value for your startup.
Thanks to Hans Westerhof and Chretien Herben.
Venture Value does startup valuations for founders who want to raise money with an investor.