Margin Call Calculator
You bought on margin. At what price does your broker start selling your shares out from under you? Know the number before the market finds it for you.
Your inputs
How margin calls work
When you buy on margin, your equity is (market value − loan) ÷ market value. The broker demands that ratio stay above the maintenance margin — FINRA's floor is 25%, though most brokers set 30–40%. The moment a falling price pushes your equity ratio to the line, you get a margin call: deposit cash or the broker liquidates your shares, without asking first. Because the loan is fixed (and growing with interest) while the market value moves, the call always arrives at one exact price — the one this calculator finds.
The math behind this calculator
Set the equity ratio equal to the maintenance margin and solve for market value. Interest accrues on the loan for every day you hold, so the call price is a moving target that rises over time.
Loan after d days = loan × (1 + interest rate)^(d/365)
Call when (MV − loan) ÷ MV = maintenance margin
→ MV at call = loan ÷ (1 − maintenance margin)
→ Call price per share = MV at call ÷ shares
Worked example
100 shares at $100 with 50% initial margin: you put up $5,000, the broker lends $5,000. At a 25% maintenance margin the call comes when the position is worth $5,000 ÷ 0.75 = $6,666.67 — a share price of $66.67, i.e. a 33.33% drop. Now hold 90 days at 8% margin interest: the loan grows to about $5,096 and the call price rises to roughly $67.94. You did nothing, the stock did nothing, and your danger line still moved up nearly $1.30 against you.
Caveats worth knowing
- Your broker's requirement beats FINRA's. The 25% here is the legal floor; most brokers demand 30–40% and can raise it on volatile stocks at any time — each hike moves your call price up with zero notice.
- They can sell without telling you. A margin agreement isn't a negotiation. Brokers may liquidate some or all of your holdings to satisfy a call, and they choose what to sell.
- Time is not neutral. Margin interest compounds against you daily, so a position that's merely flat slowly drifts toward its call price. Leverage has a carrying cost that buy-and-hold doesn't.
- Long positions only. This calculator models stock you bought with borrowed money. Short positions face the mirror-image risk — uncapped losses as prices rise — and need a different formula.
Sources: FINRA — margin maintenance requirements; Federal Reserve — Regulation T (50% initial margin).