Margin Call Calculator

Background.

Borrowing from a broker to buy shares magnifies losses as well as gains, and the margin call is where that leverage catches up with you. The rule behind it is simple: the equity in the account, meaning the market value of the securities minus what you owe the broker, must stay at or above a set percentage of that market value. FINRA Rule 4210 puts the floor at 25% for ordinary long stock positions, and many firms add a stricter house requirement on top.

Because the loan stays fixed while prices move, equity falls faster than the portfolio does. An account worth $30,000 carrying a $24,000 loan holds $6,000 of equity, which is 20%. A 25% requirement calls for $7,500, so the account is $1,500 short. That gap is the figure shown here: the cash you would need to deposit to bring equity back up to the requirement, or zero if the account already clears it.

Cash is not the only way to answer a call, and the alternative costs more than it looks. Selling shares pays down the loan but also shrinks the market value the requirement is measured against, so at 25% maintenance you would have to sell four times the shortfall, $6,000 of stock in this case.

It also helps to know how much room you start with. Buy with the 50% initial margin Regulation T requires, keep a 25% maintenance level, and the holdings can lose a third of their value before the first call.

Treat the answer as a scenario, not a demand from your broker. Firms can raise requirements on volatile or concentrated holdings and may sell your positions without waiting for a deposit. Options, short sales, intraday swings and interest charges are outside this simple equity check.

What is margin call calculator?

A margin call is a broker's demand for more equity when a margin account's equity drops below the maintenance requirement. Equity is the current market value of the securities held minus the margin loan. The maintenance shortfall is the requirement percentage multiplied by the market value, minus the current equity, and it equals the smallest cash deposit that brings the account back into line. When equity already meets or exceeds the requirement, the shortfall is zero and no call is due.

How to use this calculator.

1. 01Enter the current market value of the securities in the margin account, as your broker's statement or account screen shows it at today's prices.
2. 02Enter the current account equity: that market value minus the margin loan balance. Most brokers display it directly. It must be a positive number, so an account already worth less than its loan cannot be entered.
3. 03Enter the maintenance requirement as a percentage: 25 for the FINRA minimum on long stock, or your broker's house figure if it is higher for your holdings.
4. 04Read the shortfall as the cash deposit needed now. If you would rather sell shares, divide the shortfall by the requirement written as a decimal to see how much stock, at current prices, would have to go.

The formula.

Shortfall = max(m × V − E, 0), where V is the current market value of the securities, E the account equity and m the maintenance requirement as a fraction, so 25% becomes 0.25. The product m × V is the least equity the rule allows at today's prices; subtracting the equity you actually have leaves the deficit, and the max(…, 0) shows a well-funded account as zero rather than a negative surplus. Falling prices push the shortfall up from both sides at once. Every dollar of lost market value cuts equity by a full dollar, because the loan does not shrink, while the required equity falls by only m of that dollar. At a 25% requirement, each further $1,000 drop in market value adds $750 to the call. The page refuses a requirement above 100% and any input that is zero or negative.

A worked example.

Frequently asked questions.

References& sources.

1. [1]FINRA Rule 4210, Margin Requirements.
2. [2]SEC Investor Bulletin, Understanding Margin Accounts.
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.