Buying Power: Cash, Margin, and Leverage That Cuts Both Ways

Buying power is the number your broker shows for how much you can deploy right now — and it is frequently larger than the cash you actually own. This page separates cash buying power from margin buying power, explains how options buying power works when you buy versus sell, and walks the small-account math on why borrowed leverage magnifies losses exactly as fast as gains. Research and education only — not financial advice.

Buying power is the total dollar amount of securities you can purchase in your account at this moment. The trap is in the word can: buying power is not a measure of what you own, it is a measure of what you can control — and on a margin account those are two very different numbers. Understanding which kind of buying power you are spending is the difference between a calculated position and an accidental one.

Cash buying power: what you actually have

In a cash account, buying power is simple and honest: it equals your settled cash. No borrowing, no amplification. You can buy $3,000 of stock if you have $3,000 of settled cash, and not a dollar more.

The one wrinkle is settlement. When you sell a stock, the proceeds are not instantly re-spendable — U.S. equities settle on a T+1 basis (one business day after the trade). Buy with unsettled proceeds and then sell again before they settle and you can trigger a good-faith violation. Cash accounts trade smaller, but they cannot be forced to liquidate and they cannot go negative. The floor is zero, and that is the entire safety feature.

Margin buying power: borrowed multiplication

A margin account lets the broker lend you money against the value of your securities. Under the Federal Reserve's Regulation T, you must put up at least 50% of the purchase price for most marginable stocks, which is where the familiar figure comes from: roughly 2:1 buying power. Deposit $5,000 and you may control about $10,000 of stock — the broker fronts the rest and charges interest on it.

That borrowed half does not come free of strings. FINRA sets a maintenance margin minimum of 25% of the position's market value (brokers routinely require more), and if your equity slips below it, you get a margin call: deposit cash or the broker sells your positions for you, at prices and times of its choosing, to protect its loan. Forced liquidation is the part beginners rarely model — it converts a temporary drawdown into a permanent, involuntary exit at the worst possible moment.

Account type	Buying power source	Typical multiple	Can you be liquidated?
Cash	Settled cash only	1:1	No
Margin	Cash + broker loan vs. equities	~2:1 (Reg T)	Yes — margin call
Margin (PDT, intraday)	Day-trading buying power	up to 4:1 intraday	Yes — day-trade call

Options buying power: it depends which side you take

Options behave differently from stock, and the direction of the trade decides everything.

Buying options (long calls/puts): you pay the premium in full. There is no Reg T margin on a long option purchase — the debit is the debit. What looks like leverage here is not borrowed money; it is embedded in the contract, because one contract controls 100 shares of the underlying for a fraction of the shares' cost.
Selling options (short): now buying power is collateral. A naked short call or put ties up a substantial margin requirement against the risk you have taken on; a cash-secured put reserves the full cash needed to buy the shares if assigned; a defined-risk credit spread reserves roughly its maximum possible loss. Selling options consumes buying power in proportion to how much you could lose, not how much you paid.

The mental model: buying options spends cash equal to the premium; selling options spends buying power equal to the risk. A $200 long call costs $200. A short put on a $50 stock can reserve thousands, because that is what it would cost to make good on assignment.

Why leverage cuts both ways

Leverage is symmetric, and that symmetry is the whole lesson. Borrow to double your exposure and a 10% move in your favor becomes roughly a 20% account gain — but a 10% move against you becomes roughly a 20% loss, before interest. Options concentrate this further: a contract can gain or lose 50% of its premium on an ordinary day in the underlying. The reason so many accounts end abruptly is not that traders fail to see the upside of leverage; it is that they size against the upside and get invoiced for the downside.

Leverage does not change your edge. It changes the speed at which being wrong reaches your account balance.

The small-account reality

Here is the failure that buying power quietly enables, drawn from the worked trade in our free handbook chapter (one illustrative trade, not a performance claim). A single put position cost $728 of premium in a trading account of about $940 — roughly 92% of the tradable money in one option, on one stock, one idea, one expiration. Nothing stopped it: the buying power was there, so it got spent. A routine 50% adverse move on that position would erase about 46% of that tradable money in an afternoon.

The corrective is a sizing rule, not a bigger brain. Our desk's rulebook caps risk near 10% of the account per idea. On that same $940 balance, 10% is about $91 — one contract instead of eight, the identical thesis at survivable size. Ten percent sizing buys you roughly ten independent attempts for your edge to show up; 92% sizing buys you one coin flip with the rent. The full math lives in the sizing chapter of Options, In Plain English, and the discipline generalizes in position sizing and small-account options strategy.

One regulatory floor to know: in a margin account, making more than three day trades in five business days flags you as a pattern day trader, which requires maintaining at least $25,000 in equity. Below that, the account is restricted. It is a real constraint on how small-account buying power can be used intraday — plan around it before you trip it.

Every trigger-based card on our public desk is sized to buying power on purpose, posted before the move to a timestamped paper/model record where the losing cards stay visible. Buying power is the accelerator; sizing is the brake. You need both hands on the wheel.

Common questions

What is the difference between cash and margin buying power?

Cash buying power equals your settled cash — you can only buy what you can pay for outright, and the account cannot go negative or be liquidated. Margin buying power adds a broker loan against your securities, typically giving about 2:1 under Regulation T, but it carries interest, a maintenance requirement, and the risk of a margin call forcing you out of positions.

Does buying an option use margin?

No. Long calls and puts are paid for in full — the debit equals the premium, with no Reg T margin extended on the purchase. The leverage in a long option is embedded in the contract itself, since one contract controls 100 shares. Selling options is different: a naked or cash-secured short position reserves buying power in proportion to its risk, which can be far larger than any premium collected.

Why does leverage 'cut both ways'?

Because it is symmetric. Doubling your exposure with borrowed money roughly doubles a favorable move into a larger percentage gain — and doubles an adverse move into an equally larger percentage loss, plus interest. Leverage does not improve your edge; it only speeds up how fast being right or wrong reaches your account balance, which is why sizing matters more, not less, as leverage rises.

How much buying power do I need to day trade?

In a margin account, more than three day trades in five business days classifies you as a pattern day trader, which requires maintaining at least $25,000 in account equity. PDT accounts can access up to 4:1 intraday day-trading buying power, but that amplification comes with day-trade calls if exceeded. Cash accounts avoid the PDT rule but are limited by settlement — sold proceeds are not re-spendable until they settle.

See the process with your own eyes. The desk posts trigger-based cards to a public, timestamped record — losses included — and published the backtest where its own raw scanner loses. The scoreboard is free to watch. Join the floor →

Free to join · paid floors optional · research and education only

Last updated 2026-07-11 · ClaudeQuantAlgo Research Desk · research and education only.

Disclosures. ClaudeQuantAlgo is a research and education community. Nothing on this page constitutes financial, investment, legal, or tax advice, or a recommendation to buy or sell any security or derivative. No profit promises are made, ever — trading stocks, options, and forex involves substantial risk of loss; options positions can lose 100% of their value. The public scoreboard reflects a model ("paper") desk — no real money. Past performance — real, paper, or simulated — never guarantees future results. Hypothetical and simulated results have inherent limitations and no representation is made that any account will or is likely to achieve similar profits or losses. ClaudeQuantAlgo is not a registered investment adviser or broker-dealer. You are solely responsible for your own trading decisions. Never risk money you cannot afford to lose.