What Is Margin Equity?
Every margin account carries two numbers that matter more than its total balance: what’s actually yours, and what you still owe against it.
The short answer
Margin equity is the value of the securities held in a margin account minus the amount currently borrowed against them. It’s recalculated continuously as prices move, since the value of the holdings changes throughout the trading day even though the loan balance generally does not. Brokers rely on this figure, rather than the account’s total value, to judge whether an account still meets its required cushion.
The calculation itself
The math behind margin equity is straightforward even if the number moves constantly: total market value of everything held in the margin account, minus the outstanding loan balance. Say an account holds securities worth $20,000 and $8,000 of that was borrowed on margin — equity in that example would be $12,000. Nothing about the formula changes as prices move; only the market value side of the equation does.
Why equity shifts without any trading at all
Because the loan balance stays fixed unless money is borrowed or repaid, day-to-day changes in equity come almost entirely from price movement in the securities held. A rally in the account’s holdings increases equity, and a decline shrinks it, all while the borrowed amount sits unchanged in the background. Using the earlier example, if that $20,000 in holdings dropped to $16,000 while the $8,000 loan stayed the same, equity would fall from $12,000 to $8,000 — a 33% drop in equity from only a 20% drop in the underlying holdings. This is part of why margin accounts can feel more volatile than the same holdings would in a cash account — the loan amplifies the swing in equity relative to the swing in the underlying prices.
How equity connects to maintenance requirements
Brokers express margin equity as a percentage of the account’s total position value, and that percentage is compared against a required minimum. Suppose a broker set a maintenance requirement of 30% and an account’s equity ratio slipped to 22% after a decline in holdings — that gap is what triggers a call for more funds or securities. The margin maintenance requirement percentage itself is set by the broker, subject to regulatory minimums that can change over time, but the equity figure being measured against it is calculated the same way regardless of where the threshold sits.
Why the figure also shapes buying power
Margin equity isn’t only a warning signal — it’s also the base number brokers use when calculating how much additional purchasing power an account has. The details of that calculation, covered in how margin buying power is calculated, build directly on the equity figure, which is one reason a shrinking equity balance affects more than just the risk of a call — it can also reduce how much can be purchased going forward.
The takeaway
Margin equity is less a static number than a running total that reacts to every price change in the account. Understanding how it’s calculated, and how closely it’s tied to both maintenance requirements and buying power, makes it easier to see why brokers watch this figure so closely — and why account holders benefit from watching it too.