This sheet will help you look at different financing scenarios as well as begin to understand how venture math works. You can plug in a few founders, sketch out an option pool, and see how different valuations and round sizes affect the post-money situation. Sometimes, it’s less important than you think to worry about $4.5m pre-money vs. $5.0m.
It’s based on a spreadsheet I created myself to do exactly these calculations. There’s usually no need for a complicated model – the valuation range is normally pretty tight, the number of shares should be known or within a known range (for example, whether your first dev gets 5% or 10%). I hope you find it helpful.