Day trading buying power calculator
A pattern day trader with a US margin account can trade up to four times their maintenance margin excess during the session, but only about half of that can be held overnight. Enter equity at the last close, the maintenance margin on positions you are carrying and the stock you plan to trade, and the calculator gives your day trading buying power and the shares it buys. It shows the overnight limit too, so you know how much must be closed before the bell.
During the day and overnight
Your equity, the excess that buying power is calculated from, and how much you can hold during the session versus after the close.
Shares by maintenance requirement
Brokers set higher requirements on riskier stocks, and the higher the requirement, the fewer shares your buying power covers.
| Requirement on the stock | Intraday shares | Intraday value | Overnight shares |
|---|
How buying power is calculated
This uses the standard FINRA margin rules for pattern day traders. Your broker may set tighter limits, so check its figures before trading close to the edge.
Maintenance margin excess
Equity less the maintenance required on overnight positions.
excess = equity − held positions × their requirement
Day trading buying power
Up to four times the excess, for accounts with $25,000 or more.
DTBP = 4 × excess
Allow for the stock
Four times assumes a 25% requirement; a higher requirement buys proportionally less.
tradeable value = DTBP × 25% ÷ stock requirement
Number of shares
Value you can trade divided by the share price, rounded down.
shares = tradeable value ÷ price
Overnight
Positions held past the close need 50% initial margin, so roughly twice the excess.
overnight buying power ≈ 2 × excess
Day trading buying power FAQ
What does day trading buying power mean?
It is how much a pattern day trader can buy and sell within one session in a US margin account. Under FINRA rules it is up to four times the account's maintenance margin excess at the previous close, and it applies only to positions opened and closed the same day.
How do I calculate it?
Take equity at yesterday's close and subtract the maintenance margin on positions you held overnight; that is the excess. Multiply by four. With $40,000 equity and $6,000 maintenance on overnight positions, the excess is $34,000 and buying power is $136,000.
Why does some stock get me fewer shares?
Brokers set higher maintenance requirements on volatile, cheap or concentrated positions, sometimes 50 or even 100 percent. Each dollar of buying power then covers less of that stock, and the calculator adjusts for the requirement you enter.
What is overnight buying power?
Positions kept past the close need the standard 50 percent initial margin, so overnight buying power is usually about twice your excess, not four times. Carrying a full day trading position overnight can trigger a margin call.
What if I go over my day trading buying power?
You get a day trading margin call. Until it is met, usually within five business days, buying power may drop to two times excess, and failing to meet it can limit the account to cash trades for 90 days.
Do accounts under $25,000 have day trading buying power?
No. Below $25,000 a margin account cannot be used for pattern day trading, so the four-times figure does not apply. Use our PDT rule calculator to count the day trades left in your window instead.