A margin call occurs when the equity in your margin account falls below the broker's maintenance requirement, forcing you to either deposit more cash or sell securities to restore the account to compliance. Understanding when a margin call happens is critical for anyone using leverage in their investment account.
The Formula
Account Equity = Market Value of Securities - Borrowed Amount
Margin Percentage = Account Equity / Market Value of Securities
A margin call is triggered when Margin Percentage < Maintenance Requirement (typically 25-30%).
The minimum value before a margin call is:
Minimum Security Value = Borrowed Amount / (1 - Maintenance Requirement)
Worked Example
You buy $10,000 of stock using 50% margin (borrowing $5,000):
- Initial security value: $10,000
- Borrowed: $5,000
- Initial equity: $5,000
- Initial margin: 50%
Your broker requires 30% maintenance margin. The margin call level is:
Minimum Value = $5,000 / (1 - 0.30) = $5,000 / 0.70 = $7,142.86
If the stock value falls to $7,100, your equity becomes $7,100 - $5,000 = $2,100, and your margin percentage is $2,100 / $7,100 = 29.6%, below the 30% requirement. You receive a margin call and must deposit $142.86 or sell securities.
The Cascade Effect
Margin calls are particularly dangerous in rapidly falling markets. When prices drop, account equity shrinks, triggering calls. If you can't meet them, forced sales push prices lower, triggering more calls โ a cascade that can wipe out your equity quickly.
Key Leverage Points
| Initial Margin | Maximum Leverage |
|---|---|
| 50% | 2:1 |
| 33% | 3:1 |
| 25% | 4:1 |
| 20% | 5:1 |
Lower initial margin means higher leverage, which amplifies both gains and losses.
Risk Management
Margin allows you to control more capital with less cash, magnifying returns โ but also losses. A 20% decline in security value can wipe out 100% of your capital if you're on 5:1 margin. Always maintain a buffer above maintenance margin and have a plan for funding a call before it happens.
Tips
Track your account equity daily if using margin. Set personal margin limits stricter than your broker's requirements to give yourself a safety margin. Remember that margin interest also erodes returns โ margin is most appropriate for short-term trading, not long-term buy-and-hold investing.
Use our Margin Call Calculator to see what security values trigger a call in your account.