At the top of your Investing tab, you'll see how much capital you have available to invest now. We refer to this as "Investable Now."
You can see how this is calculated by clicking on the blue Capital Breakdown link in the top righthand corner. We calculate it by subtracting how much you've invested, your management fees, and AngelList admin fees from the total amount of capital you've closed.
This number automatically updates when your investments close or you receive more capital– check back if you're ever unsure of how much you have available to invest.