How do I calculate how many shares to give someone to equal a given % equity?

You want to give someone, say, 10% equity, here's how to calculate how many shares to give them. 

Assuming you have N shares
and you want to give someone X% equity
then the number of shares to give them is N * X/(100-X)

For example:

• you have 100,000 shares

• you want to give someone 10% equity

• then you'll give them 100,000 * 10/90 = 11,111 shares

After you've given them their shares, they'll have 11,1111 out of 111,111 total shares = 10% equity.

Easy once you know the formula!

When you do a funding round on SeedLegals the platform works this all out for you, automatically updating all the numbers for you as you add/remove investors, change the valuation, etc.

But, if you're, say, giving equity to a new team member outside of a funding round then you'll need to do that calculation yourself and then add that person and their shares in a new Historic Round (or an existing one, as needed).