What Is a Margin Account? How It Works With an Example

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A margin account is a brokerage account in which the broker lends you money against the cash and securities you hold, so you can buy positions larger than your own funds or sell securities short. The assets in the account serve as collateral for the loan. Because you control more than you deposited, gains and losses are both measured against a smaller equity base, and they move faster than they would in a cash account.

In forex and CFD trading, the term works differently: “margin” is usually a good-faith deposit that a broker sets aside to open a leveraged position, rather than a loan with a stated interest rate.

How a Margin Account Works

Opening the account

In the U.S., FINRA rules require at least $2,000 in equity (or the full purchase price, if lower) before a customer can trade on margin. You sign a margin agreement, which gives the broker a lien on the securities in the account and the right to sell them to protect the loan. Brokers also screen applicants on factors such as income, net worth and trading experience, and they can decline or limit margin privileges.

Traders who make four or more day trades within five business days in a margin account are classified as pattern day traders. That label requires minimum equity of $25,000 in the account; below that level, day trading is restricted. Retirement accounts such as traditional and Roth IRAs generally cannot borrow on margin.

Buying power and leverage

Under Regulation T, you can borrow up to 50% of the purchase price of eligible stocks. With $10,000 of your own money, you could buy up to $20,000 of marginable shares, which doubles your buying power.

That doubling applies to results as well. If the $20,000 position rises 10%, the $2,000 gain is 20% of your $10,000 equity. If it falls 10%, you lose 20% of your equity. Not every security is marginable. Brokers can exclude low-priced stocks or volatile issues, or apply higher requirements to them.

The core formulas

Three numbers describe a long margin position at any moment:

• Market value = shares held × current price
• Loan balance = amount borrowed + accrued interest not yet paid
• Equity = market value − loan balance

Your equity percentage is equity ÷ market value. The broker compares this figure with the maintenance requirement. When the price falls, the loan stays the same, so the entire loss comes out of your equity, and the percentage drops faster than the price.

For a short sale, the logic is reversed. When you short, the sale proceeds plus your required deposit sit in the account as a credit balance, and:

• Short equity = credit balance − current market value of the shorted shares

A rising share price increases the cost of buying the shares back and reduces equity, so a short position can come under a margin call as the price climbs.

Interest and costs

Brokers calculate interest daily on the borrowed balance and typically charge it monthly, usually as a spread over the broker’s base rate, often lower for larger balances. Interest is a fixed drag: if a position moves sideways for months, the account loses money even though the price has not changed, and higher benchmark rates raise that cost further.

Margin Requirements and Margin Calls

Two thresholds govern a margin account:

• Initial margin: the share of the purchase you must fund yourself. Regulation T sets this at 50% for most stocks.
• Maintenance margin: the minimum equity you must keep while the position is open. FINRA’s floor is 25% of the market value of securities held long, and many brokers require 30% to 40% or more, especially on concentrated or volatile holdings.

If equity falls below the maintenance level, the broker issues a margin call: you must deposit cash or securities, or reduce the position. Brokers often allow a few business days, but the margin agreement usually lets them act sooner, and in fast markets they may liquidate without waiting. The broker chooses which positions to sell and when, so a forced sale can realize losses at the worst point of a move.

Example of a Margin Account

Hypothetical example. Ignores interest, commissions and taxes; assumes a 50% initial and 25% maintenance requirement.

An investor deposits $30,000 and wants to buy XYZ stock at $100 per share.

• Cash only: 300 shares ($30,000 ÷ $100).
• On margin: 600 shares ($60,000), funded with $30,000 of equity and a $30,000 loan.

If the price rises to $120:

• Market value: $72,000
• Gain: $12,000; equity becomes $42,000
• Return on equity: 40% (versus 20% without margin)

If the price falls to $80:

• Market value: $48,000
• Loss: $12,000; equity becomes $18,000
• Loss on equity: 40% (versus 20% without margin)
• Equity percentage: $18,000 ÷ $48,000 = 37.5%, still above 25%

Where the margin call starts. The call price for a long position is:

Call price = loan ÷ [shares × (1 − maintenance requirement)]

Here: $30,000 ÷ (600 × 0.75) = $66.67. At that price the shares are worth $40,000, equity is $10,000, and $10,000 is exactly 25% of $40,000. Any further decline triggers a call. With a 40% house requirement, the call price rises to $30,000 ÷ (600 × 0.60) = $83.33, so the same trade would be under pressure much sooner.

If the stock gapped down to $45 overnight, the shares would be worth $27,000 against a $30,000 loan. The investor would have lost the whole deposit and still owe the broker $3,000.

Margin Accounts in Forex and CFD Trading

Retail forex accounts are often called margin accounts because every position is leveraged, but the mechanics use different terms:

• Required (used) margin is the deposit set aside to open a position, expressed as a percentage of notional value. A 2% requirement corresponds to 50:1 leverage.
• Equity is balance plus or minus open profit and loss. Balance only changes when trades close, so the two can diverge sharply.
• Free margin = equity − used margin, the amount available for new positions.
• Margin level = equity ÷ used margin × 100%.

Hypothetical example: a $10,000 account opens one standard lot of EUR/USD at 1.1000, a notional value of $110,000. At a 2% requirement, used margin is $2,200, free margin is $7,800 and margin level is about 455%. If the position loses $7,000, equity falls to $3,000 and margin level to about 136%. Each broker sets its own margin call and stop-out levels; at stop-out, the platform closes positions automatically, usually starting with the largest loser.

In the U.S., CFTC and NFA rules cap retail forex leverage at 50:1 on major currency pairs and 20:1 on others; other jurisdictions set their own limits. Instead of margin interest, positions held overnight are credited or debited a rollover (swap) based on the interest rate differential between the two currencies. Sizing trades by risk rather than by available margin is the main defense; a position size calculator converts a stop distance and risk percentage into a lot size.

Margin Account vs. Related Terms

• Margin account vs. cash account: a cash account requires full payment for purchases and does not allow short selling. Many brokers also apply settlement rules to cash accounts that limit how quickly sale proceeds can be reused.
• Margin vs. leverage: margin is the equity you must post; leverage is the ratio of position size to that equity. A 50% initial margin equals 2:1 leverage; a 2% forex margin equals 50:1.
• Initial vs. maintenance margin: meeting the initial requirement when you open a position does not guarantee you meet maintenance after prices move.
• Margin call vs. stop-out: a margin call is a demand for more equity; a stop-out is the broker closing positions when equity is not restored or falls below a hard threshold.

Limitations and Risks

• Amplified losses: a 10% decline in holdings bought with 50% margin is a 20% loss of equity, and gaps can push losses past your deposit.
• Loss of control: the broker decides when and what to liquidate, and can raise house requirements without advance notice.
• Interest drag: interest accumulates whether or not the trade works.
• Behavioral pressure: leveraged positions in volatile sessions can push traders into decisions they would not make with unleveraged money, and strategies that add to losing positions, such as the martingale approach, become especially dangerous.

A stop-loss order can cap a planned loss on many trades, but once triggered it becomes a market order, so in a gap the fill can be well beyond the stop price.

FAQs

The Bottom Line

Margin accounts matter to stock investors seeking more buying power and to forex and CFD traders, whose positions are always leveraged. Borrowing magnifies losses as much as gains, adds interest costs, and lets the broker sell positions on its own terms, so a sharp gap can wipe out a deposit and leave a debt. Sizing trades by risk rather than by available margin is the main defense.