Calculate the stock price that triggers a margin call from your purchase price, initial margin, and maintenance margin requirement, plus the drop percentage.
Margin Call Price Formula
A margin call triggers when your equity falls to the maintenance requirement. For a stock bought on margin, the trigger price is:
MCP = P0 * (1 - IM) / (1 - MM)
Starting from dollar amounts instead, the account value that triggers a call is:
CallValue = Loan / (1 - MM)
Variables:
- MCP is the margin call price per share ($)
- P0 is the purchase price per share ($)
- IM is the initial margin as a decimal (0.50 for the standard 50%)
- MM is the maintenance margin as a decimal (0.25 for a typical 25%)
- Loan is the margin loan balance ($)
The logic: the borrowed amount per share is fixed at P0 * (1 – IM), while your equity is whatever the share price is above that loan. Equity divided by price equals the maintenance requirement exactly at the margin call price. Choose the percentage mode if you know your margin terms, or the dollar mode if you’d rather enter your current market value and loan balance – the calculator returns the trigger level, how far away it is, and your equity at that point.
Margin Call Price by Maintenance Requirement
For a $100 stock bought at 50% initial margin ($50 borrowed per share), this is where a call triggers at common maintenance levels.
| Maintenance margin | Margin call price | Drop required |
|---|---|---|
| 25% (FINRA minimum) | $66.67 | 33.3% |
| 30% (common broker default) | $71.43 | 28.6% |
| 35% | $76.92 | 23.1% |
| 40% (volatile stocks) | $83.33 | 16.7% |
| 50% | $100.00 | 0% – already at the line |
Higher maintenance requirements move the trigger closer to your purchase price – at 50% maintenance on 50% initial margin there is no cushion at all.
Example Problems
Example 1: Standard 50/25 terms.
You buy shares at $80 with 50% initial margin and a 25% maintenance requirement.
MCP = 80 * (1 – 0.50) / (1 – 0.25) = 80 * 0.50 / 0.75 = $53.33. The stock can fall 33.3% before a call. Your borrowed amount is $40 per share, and at $53.33 your equity is $13.33 – exactly 25% of the position value.
Example 2: Dollar mode.
Your account holds $20,000 of stock against a $10,000 loan with 30% maintenance.
CallValue = 10,000 / (1 – 0.30) = $14,286. The portfolio can fall 28.6% before the call; at that point your equity is $4,286.
Frequently Asked Questions
What happens when I get a margin call?
Your broker demands you restore the maintenance level – by depositing cash, adding marginable securities, or selling positions – usually within two to five business days. Brokers reserve the right to liquidate your positions without notice if the deficit grows.
Why is my broker’s requirement higher than 25%?
FINRA’s 25% is a floor, not the norm. Brokers routinely set 30% to 40% house requirements and raise them further on volatile, concentrated, or low-priced positions – sometimes to 100%, which removes margin eligibility entirely.
Does the margin call price change over time?
Yes. Margin interest accrues to your loan balance, dividends and deposits raise your equity, and brokers change house requirements. Recompute whenever your loan balance or the requirement moves – the trigger price rises as interest compounds.
