Core terms
Buying power
The value of securities an account can currently buy or sell short, as the broker calculates it from cash, margin rules and house requirements.
Buying power is a broker's number, not a regulator's. A cash account's buying power is roughly its settled cash. A margin account's is larger, because the broker lends against the account, and it changes during the day as positions open and close and as the broker applies its own requirements to each stock.
Under FINRA's intraday margin standards, effective June 4, 2026 with firm phase-in allowed until October 20, 2027, brokers measure an "intraday margin deficit" on days with trades that reduce what you could withdraw. How each broker turns that into a buying-power figure varies.
What traders should verify
Size positions from risk per trade, not from buying power. Buying power says how much you may trade, not how much you should.
Do not conflate
Displayed buying power can drop suddenly when a broker raises a stock's house requirement, for example after a large move.