(Updated: See comment from Dave Lavinsky below for an update on a minor flaw that has been fixed, plus some helpful context about some other things the calculator does not take into account.)

calculator2.bmpReader Dave Lavinsky has created a nifty calculator for entrepreneurs wanting to know how their seed and subsequent rounds affect their ownership in a start-up.

He calculates the seed round on the “QuickStart” formula popularized by Charles River Ventures, which we wrote about last week. CRV is writing small checks in return to start-ups in exchange for getting a discount on an investment in a company’s first round.

The calculator allows up to 5 rounds of financing and shows the equity that the management team, CRV (in this case), and other investors get. You can view the calculator here.