FWIW, 1) I focus on three numbers: net liq., available margin, and "cushion" (you have to hunt for "cushion", but it's available on your TWS dashboard). 2) I focus on $5 "slots" of margin -- I take net liq., divide by $5*100 (SPX; 50 for ES; etc etc), and I have the number of $5 slots that the account can support ON ONE SIDE. 3) $5 slots of margin can also be parachutes. If a position is assailed from one side, and you judge the risk prudent, you can buy out the position, move down 2-3 strikes, deploy a second set of slots (another parachute), and remain revenue-neutral. [You HAVE doubled your risk.] 5 such parachutes -- 5 such doubling of margined capital -- is 32x your original position. As a starting rule, writing 1/32nd of your account leaves room for 5 doublings. If you roll out in time instead of away from market, modify to suit. (At this point, you want to introduce Mr. Kelly to Mr. Markov, and have them set some rules for you.) 4) IB counts put-devoted margin against higher strike call positions, and vice-versa, PER EXPIRY. That is, margin put up to support put verticals will similarly support the call-side BWBs above it -- provided the BWBs require the same number of $5 slots or less. (I'm sure this sounds familiar.) 5) 5 $5 SPX put spreads for Dec23 will require $2500 of margin; 5 $5 call spreads of Dec30 will require an additional $2500 of margin. Thus, you could write UP TO 5 $5 call spreads for Dec23 and/or, UP TO 5 additional $5 put spreads for Dec30, for no additional margin burden. 6) ES (being a CFTC beast) is handled quite differently; its margining is a black art, known as Sauron Pfarts Around {with} Numbers, or SPAN for short. Google SPAN. Do NOT try to analyze it; do NOT try to predict HOW, OR WHEN, it is applied. Just know that it is actuated by Murphy, and will seek to hit you at the worst possible. (But if you counter a new set of ES spreads in on expiry with an opposite-side set IN ANOTHER EXPIRY, and see no new margin burden, then you'll know a big diff between the CFTC and the SEC. I'd say, but I forget.) Hope that clears some things up. Oh, and 7) Tom Sosnoff handles risk the way a blind taxi driver handles the Indy500: "Drive fast. When you hear lots of jarring and grating sounds, turn left. When the noise stops, straighten the wheel again."