Impact of a new round on founder ownership

What I did: Modeled what a Series B would do to founder ownership before signing a term sheet.

The prompt I used:

If [Company Name] raises a $[X]M Series [A/B] at a pre-money valuation of $[Y]M, what will the founders' ownership be post-money on a fully diluted basis, assuming a standard 14% option pool top-up?

Result: A before/after dilution table showing exactly what the round would cost in ownership — We can run three valuation scenarios in about 5 minutes.