If you’ve ever logged into your brokerage account and noticed a number labeled “buying power” that’s higher than your actual cash balance, you’ve likely wondered where that extra figure comes from. Buying power is one of the most fundamental — and frequently misunderstood — concepts in stock trading, and understanding it thoroughly can help you avoid costly mistakes as you build your portfolio.
At its core, buying power represents the total dollar amount you have available to purchase securities at any given moment. But depending on your account type, that number can mean very different things, and misunderstanding it can lead to unexpected margin calls, failed trades, or unintended leverage.
This guide breaks down exactly what buying power is, how it’s calculated, and what every trader should know before relying on it to make investment decisions.
“Buying power tells you what you can spend — it doesn’t tell you what you should spend.”
— Infinity Capital Group
Defining Buying Power
Buying power is the total amount of money available in your brokerage account to purchase securities at any given time. In its simplest form, in a standard cash account, buying power is essentially equal to your available cash balance — the money you’ve deposited and haven’t yet used to buy other investments.
However, in a margin account, buying power can be significantly higher than your actual cash balance, because it includes borrowed funds made available by your brokerage. This is where buying power becomes more nuanced, and where many new traders can misunderstand exactly how much risk they’re taking on.
Understanding which type of account you have — and how buying power is calculated within it — is the first step toward using this figure responsibly.
Cash Account Buying Power
In a cash account, buying power is fairly straightforward. It reflects the actual cash you’ve deposited, plus any proceeds from securities you’ve already sold, minus any funds tied up in pending or unsettled trades.
One important nuance in cash accounts is settlement time. When you sell a security, the proceeds aren’t always immediately available to reinvest — they typically need to settle first, a process that can take a set number of business days depending on the security type and your brokerage’s policies.
This means your buying power in a cash account can sometimes be lower than your total account value on paper, simply because a portion of your funds are still in the process of settling from a recent sale.
Margin Account Buying Power
In a margin account, buying power is calculated differently, and it’s typically much higher than your cash balance alone. This is because margin accounts allow you to borrow funds from your brokerage, using your existing holdings as collateral, to purchase additional securities beyond what your cash alone would support.
For a standard margin account, brokerages commonly allow buying power of up to two times your account equity — meaning if you have $10,000 in equity, you may have up to $20,000 in buying power available for stock purchases. This ratio can vary depending on your brokerage, the specific securities involved, and your account’s classification.
It’s important to understand that any purchase made using this borrowed buying power represents a margin loan, which accrues interest and is subject to the maintenance requirements and margin call risks that come with any leveraged position.
“The number on your screen isn’t free money — every dollar of borrowed buying power is a dollar someone expects back, with interest.”
— Infinity Capital Group
Day Trading Buying Power
For traders classified as Pattern Day Traders — those who execute four or more day trades within five business days — buying power calculations shift again. Traders who maintain the required $25,000 minimum equity are often granted day trading buying power of up to four times their maintenance margin excess, specifically for trades opened and closed within the same trading day.
This elevated buying power reflects the reduced overnight risk associated with day trading, since positions are typically closed before the market closes rather than held open for multiple days. However, it also means that losses can accumulate more quickly within a single trading session if trades move against the trader.
Understanding the distinction between standard margin buying power and day trading buying power is essential for active traders, since these figures often differ significantly and are subject to different rules and risk profiles.
How Buying Power Changes Throughout the Day
Buying power isn’t a fixed number — it fluctuates based on your account’s activity and the current market value of your holdings. As the value of securities you own rises or falls, your account equity changes accordingly, which in turn affects how much buying power is available, particularly in margin accounts.
Placing new trades, receiving dividend payments, or having a pending trade settle can also change your buying power in real time. This is why experienced traders regularly check their buying power before executing a trade, rather than relying on figures from earlier in the trading session.
Because buying power can shift throughout the day, especially during periods of market volatility, traders using margin should be particularly cautious about assuming their available buying power will remain constant.
The Risk of Overusing Buying Power
Just because buying power is available doesn’t mean it should be fully used. Because margin-based buying power represents borrowed capital, using all of it to open the largest possible position significantly increases the risk of a margin call if the value of your holdings declines.
Traders who consistently use their full buying power leave themselves little room to absorb normal market fluctuations, since even a modest decline in portfolio value can push their account equity below the maintenance margin threshold required by their brokerage.
A more conservative approach — using only a portion of available buying power, particularly in a margin account — can provide a meaningful cushion against volatility, reducing the likelihood of a forced liquidation during a market downturn.
How Buying Power Relates to Margin Calls
Buying power and margin calls are closely connected concepts. When you use margin-based buying power to open a position, you’re increasing your account’s leverage, which also increases your exposure to potential margin calls if the value of your holdings declines.
If your account equity falls below the maintenance margin requirement set by your brokerage, you may be required to deposit additional funds or sell holdings to restore compliance — regardless of how much buying power your account previously displayed. In other words, having high buying power today doesn’t protect you from a margin call tomorrow if market conditions shift.
This relationship underscores why understanding buying power in isolation isn’t enough — it needs to be considered alongside your overall risk tolerance, your account’s maintenance requirements, and your broader trading strategy.
“High buying power and low risk tolerance make an uncomfortable combination — know which one is really guiding your trades.”
— Infinity Capital Group
Buying Power for Options and Other Securities
Buying power calculations can vary depending on the type of security being traded. Options, for example, often have their own specific buying power requirements that differ from standard stock purchases, reflecting the unique risk profile associated with options contracts.
Similarly, certain volatile or lower-priced securities may have different margin requirements applied to them, which can reduce the effective buying power available for those specific trades, even if your overall account buying power appears high.
Because these requirements can vary significantly by security type and brokerage policy, it’s important to review your specific brokerage’s documentation regarding buying power calculations for the particular securities you intend to trade.
Practical Tips for Managing Buying Power Wisely
One practical habit is to treat your margin-based buying power as a resource to be used selectively, rather than a default target to reach with every trade. Reserving a portion of your buying power as a buffer can help protect against unexpected market volatility.
Regularly monitoring your account equity relative to your maintenance margin requirement — rather than focusing solely on the buying power figure — can also provide a clearer picture of your actual risk exposure at any given time.
Finally, understanding your brokerage’s specific policies around buying power, margin calls, and day trading requirements before you begin actively trading can help you avoid unpleasant surprises and make more informed decisions about how much of your available buying power to actually use.
Final Thoughts
Buying power is one of the most important figures displayed in any trading account, but it’s also one of the most commonly misunderstood. Whether you’re working with a straightforward cash account or a leveraged margin account, understanding exactly where your buying power comes from — and what using it actually means — is essential to trading responsibly.
Buying power represents opportunity, but in margin accounts, it also represents borrowed risk. Understanding the difference, and using that buying power selectively rather than fully, can make a meaningful difference in how well your account withstands market volatility over time.
At Infinity Capital Group, we believe that understanding the mechanics behind every number in your trading account — not just the headline figures — is essential to making informed, confident investment decisions. Buying power is a powerful tool, but only when it’s fully understood.