This has been asked and answered frequently on HN. Some summaries: 1) There is no standard answer. 1% might be perfectly appropriate in this scenario, and 80

This has been asked and answered frequently on HN. Some summaries: 1) There is no standard answer. 1% might be perfectly appropriate in this scenario, and 80% might be perfectly appropriate. You should probably be looking more at ratios of His Stock:Your Stock vs. finite percentage numbers (which are basically data in a vacuum). 2) You will generally find that the "approacher" will maintain a higher stock percentage than the "approachee". Not always, but frequently. In this scenario (and the limited information provided) it appears that the "idea" guy has (at least in theory) many "tech guys" to choose from. You, based on the post here, have a single "idea guy" in front of you to partner with. Hopefully the rest of the supply and demand concept is obvious enough here that I don't have to type it all out. 3) These scenarios somewhat follow the "if you have to ask, you can't afford it" principle. If you don't know what you're worth, or how to handle this, you are probably relatively inexperienced in this particular realm of business. The experience in this case is most likely worth 10x long-term what any delta in equity between what he offers and what you think you deserve would be equal to. Track-record and experience is a very valuable thing long-term. Opportunities to get involved in a founder-type role are somewhat rare and also valuable. This is also assuming that he has at least some experience or talent pool to draw from that leads you to believe that partnering with him offers you some probably of success above and beyond any random guy with a cocktail napkin. 4) EVERYTHING is ALWAYS renegotiable. Sometimes the best way to get to where you want to be is to get on-board, prove your value, and then renegotiate at the next funding round.