About the Margin Call Calculator
This margin call calculator tells you how far a stock can move before your broker issues a margin call. Enter the purchase price, the number of shares, the initial margin you put up and the maintenance margin requirement, and it returns the margin call price, the percentage move that triggers it, your loan or short credit and your equity. Add the current price to see your equity percentage today and the cash you would need to deposit if you are already below maintenance.
It works for both long positions bought on margin and short sales. Under the Federal Reserve’s Regulation T you can typically borrow up to 50% of a purchase, and FINRA Rule 4210 requires equity of at least 25% of the market value for long positions and 30% for most short positions — though many brokers set higher “house” requirements of 30%–40% or more for volatile stocks.
The calculation covers a single position and ignores accrued margin interest, dividends and other holdings in the account, all of which change your real equity. Brokers can also liquidate positions without waiting for you to meet a call, so leave a buffer well above the trigger price.
With the default inputs, the margin call price is $66.67. Change any value above to recalculate instantly.
How to use the margin call calculator
- 1Choose long (bought on margin) or short sale.
- 2Enter the entry price and the number of shares.
- 3Enter the initial margin you put up (50% under Regulation T) and your broker’s maintenance requirement.
- 4Read the margin call price and how far the stock must move to reach it.
- 5Enter today’s price to see your equity percentage and any cash needed.
Formula and method
For a long position the loan is the purchase value minus your initial equity. Equity at any price P is P × shares − loan, and a margin call occurs when equity ÷ market value drops to the maintenance margin MM. Solving (P × N − Loan) ÷ (P × N) = MM gives P = Loan ÷ [N × (1 − MM)].
For a short sale the account holds a credit balance equal to the sale proceeds plus your initial margin deposit. Equity is that credit minus the cost to buy the shares back, P × N, and the call price solves (Credit − P × N) ÷ (P × N) = MM, giving P = Credit ÷ [N × (1 + MM)]. The cash needed to meet a call is the shortfall MM × market value − equity; depositing it restores equity to the maintenance level.
- Loan
- Entry price × shares × (1 − initial margin)
- Credit
- Short sale proceeds × (1 + initial margin)
- MM
- Maintenance margin requirement (decimal)
- N
- Number of shares
Worked examples
200 shares at $100 with 50% initial and 25% maintenance
Buying $20,000 of stock with $10,000 of your own money leaves a $10,000 loan. A call comes when 200 × P − $10,000 = 25% of 200 × P, i.e. P = $10,000 ÷ (200 × 0.75) = $66.67, a 33.3% fall. At $80 your equity is $6,000, or 37.5% — still above the requirement.
Already below a 35% house requirement
With a 35% house requirement the trigger is $10,000 ÷ (200 × 0.65) = $76.92. At $70 the position is worth $14,000 and equity is $4,000 (28.6%). The broker wants 35% × $14,000 = $4,900, so you need to deposit $900.
Short 500 shares at $40, 30% maintenance
Shorting $20,000 of stock and depositing 50% creates a $30,000 credit balance. A call comes when $30,000 − 500 × P = 30% of 500 × P, so P = $30,000 ÷ (500 × 1.3) = $46.15, a 15.4% rise. At $42 equity is $9,000, 42.9% of the position.
Frequently asked questions
How do you calculate the margin call price?+
For a long position, divide the margin loan by the number of shares times (1 − maintenance margin). With a $10,000 loan on 200 shares and 25% maintenance, the call price is $10,000 ÷ (200 × 0.75) = $66.67.
What is the maintenance margin requirement?+
It is the minimum equity you must keep in a margin account as a percentage of the market value of your securities. FINRA Rule 4210 sets a floor of 25% for long stock positions and generally 30% for short positions, but brokers often set higher house requirements, especially for volatile or concentrated holdings.
What happens if I don’t meet a margin call?+
Your broker can sell your securities — often without contacting you first and at a time it chooses — to bring the account back above the requirement. You remain responsible for any deficit if the sale does not cover the loan.
How much cash do I need to meet a margin call?+
Enough to bring equity back up to the maintenance level: maintenance % × current market value − current equity. Selling securities also works, but you must sell more than the shortfall because selling reduces the market value as well as the loan.
Why does a short position have a different formula?+
When you short, losses come from the price rising. Your account holds the sale proceeds plus your deposit as a credit, and equity is that credit minus the cost to buy the shares back. The call price therefore divides the credit by shares × (1 + maintenance margin).
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.