Buying power (BP) is the amount of funds you can use to purchase stock intraday.
The entire balance of your account, including all cash and all securities positions, less the outstanding margin debit balance.
Shares X current price.
e.g. 1,000 shares of MSFT @ 120 = MV of $120,000
That part of the value of your securities positions withheld from your equity when calculating buying power. Please note that all DTBP figures are calculated pursuant to the minimum maintenance requirements which are shown above.
30% of MV for long reduced margin eligible securities positions
e.g. long 1,000 MSFT @ 120
MV = $120,000
MRDTB = $36,000
30% of MV or $5 a share (whichever is greater) for short securities positions
e.g. short 1,000 MSFT @ 120
MV = $120,000
MRDTB = $36,000
100% of cash positions (penny stocks [stocks under $5] bulletin board securities, etc.)
e.g. long 1000 SPAZ (penny stock) @ 4
MV = $4,000
MRDTB = $4,000
Equity - maintenance requirements for trading buying power.
300% of maintenance excess, or maintenance excess x 3.
At the end of every day, each stock you are holding overnight gets marked to the market. This means that any positions you are carrying overnight will be valued at the official closing bell price and your equity will be raised or lowered accordingly. Essentially your account is given a value which is based on any cash (or debits) plus the current value of your positions (marked to market).