Margin call calculator
Find the exact price and percentage drop that triggers a maintenance margin call on a long position. The formula is P_call = loan per share ÷ (1 − maintenance rate), the same one worked out in the margin call article.
What the numbers mean
Your broker lends you the part of the purchase you did not fund. That loan does not shrink when the price falls, so your equity absorbs the whole move. The call fires when equity divided by the current market value drops under the maintenance requirement. Because the denominator falls with the price, the trigger arrives earlier than most people expect.
Assumptions
- One long equity position, no other holdings, no dividends, no accrued interest, no options.
- Maintenance requirement is your broker's house rule. FINRA's floor is 25%; brokers commonly set 30% to 40%, and higher on concentrated or volatile names.
- Margin interest is ignored. Interest accrual moves the trigger slightly closer over time.
- Illustration only, not advice. See the disclaimer.