Ask HN: Assistance determining seed round equity for advisors/angel investors

I would like to know if there are any spreadsheets I can use which have prefilled cap table calculations to help me determine equity distribution to investors and advisors during the seed round.

For example, say you determined to give out 15% equity for your seed funding but you are obtaining the total amount of funding from multiple investors, what can I use to assist me in making sure that I do not give up too much equity to each investor.