Futures Margin: The Difference Between Initial and Maintenance Requirements

A trader we’ll call Claudia funds a futures account with $25,000, and on a Tuesday morning in March buys one E-mini S&P 500 contract with the index at 5,000. Her broker shows $18,000 of initial margin held and a maintenance requirement of $16,400. She wants to know one thing before lunch: how far can this go against her before the phone rings?

172 points. That’s the answer, and here is the arithmetic behind it. Her equity is $25,000. The maintenance floor on one contract is $16,400. The difference, $8,600, is her excess. Each index point costs $50 on one E-mini, per the CME Group contract specifications. So $8,600 divided by $50 is 172 index points of room, and the call comes when the index prints 4,828.

Three lines. Equity minus maintenance, divided by dollars per point. Everything else in this piece is that formula pointed at different situations.

The two numbers do different jobs

Initial margin is a gate. It is tested once, at the moment you open, and it decides whether the trade happens at all. Claudia needed $18,000 to click buy.

Maintenance margin is a tripwire, and it never stops being tested. Futures mark to market at every settlement, cash actually moves through the clearing house, and your equity is re-measured against the maintenance floor each time. Fall below it by a dollar and you are in call territory.

The gap between the two is what people misread. With $18,000 initial and $16,400 maintenance, the gap is $1,600, which is 32 index points. A trader who funds exactly $18,000 and opens one contract has 32 points of room. Not 360 points, which is what “$18,000 of margin” sounds like to someone who hasn’t done the subtraction.

One thing worth saying plainly: the $18,000 and $16,400 here are round working numbers used to show mechanics. CME sets exchange margin through a risk model and revises it, sometimes mid-week, when volatility jumps. Your broker’s figure will differ. The formula is exact; the inputs are yours to look up.

Adding contracts eats your room twice

Claudia does well for a month and scales to three contracts, still on $25,000 — except she can’t, because three contracts need $54,000 of initial margin. So say she funds up to $60,000 and buys three.

Her cushion is not three times better. It is worse. Maintenance is now 3 × $16,400 = $49,200, leaving $10,800 of excess. And every point now costs $150, not $50. $10,800 ÷ $150 = 72 points.

She tripled her size, more than doubled her equity, and her room shrank from 172 points to 72. That’s the shape of the whole thing: contracts raise the floor and raise the burn rate simultaneously, so cushions collapse along a row rather than sliding.

Here is that collapse across account sizes. Each cell is the adverse index move that triggers a maintenance call. A dash means the account can’t open that many contracts at $18,000 initial each.

Build any cell yourself to check it. Take $200,000 with six contracts: maintenance is 6 × $16,400 = $98,400, excess is $101,600, dollars per point is $300, and $101,600 ÷ $300 = 338 points.

Look down the 172-point diagonal. $25,000 with one, $50,000 with two, $75,000 with three, $100,000 with four. Doubling equity and doubling size leaves you in exactly the same place. Room comes from equity you don’t deploy, not from equity.

Where small accounts actually die

$20,000, one contract, 72 points of room. The S&P 500 has moved 72 points intraday on plenty of unremarkable days — no crisis, no headline, just an ordinary session with a bit of range in it.

That is the common death, and it isn’t a bad thesis. It’s a correct thesis with no room to be early. The trader gets liquidated at 4,928, then watches the index close at 5,010.

The ratio matters only if you’re small

Maintenance isn’t always 91% of initial. Exchanges and brokers set the ratio, and products differ. Holding one contract and $18,000 initial fixed, here is what happens when the maintenance percentage moves:

Each column step shifts every row by a flat 18 points, because 5 percentage points of $18,000 is $900, and $900 ÷ $50 = 18. Flat shifts are devastating to a small number and invisible next to a large one. The $20,000 account goes from 130 points to 40 — better than a threefold difference. The $100,000 account goes from 1,730 to 1,640, which it will never notice.

The obvious objection: nobody holds $100,000 and trades one contract. True. Scale the contracts to the equity and you land back in the tight rows, where the ratio bites again.

Buying room, priced out

Flip the formula when the question is “how much do I need.” To survive a move of P points on N contracts:

Required equity = (N × maintenance) + (P × N × $50)

Claudia wants to hold through 200 points on one contract. That’s $16,400 + (200 × $50) = $26,400. She has $25,000, so she is $1,400 short of her own stated tolerance — which is a more useful thing to learn on a Tuesday morning than on a Thursday afternoon.

Note the top-left cell. $18,900 for fifty points of room on one contract — which is above the $18,000 needed to open. Fund exactly the initial requirement and you are inside fifty points of a call the instant you’re filled. There is no volume discount on room, either: every column is a clean multiple of the first.

The call is bigger than the shortfall

Say Claudia had funded $18,500 instead of $25,000. Her cushion is ($18,500 − $16,400) ÷ $50 = 42 points. The index drops 50 points against her, costing $2,500, and her equity lands at $16,000.

She is $400 under the maintenance floor. Her call is $2,000.

That’s because the call restores you to initial, not to maintenance. The broker is walking her from $16,000 back to $18,000, not back to $16,400. Five times the shortfall, and this is the single most reliable surprise in futures margin.

If she can’t wire it, the broker can liquidate, and futures brokers often do so intraday without waiting for the close. The SEC’s investor publication on margin makes the parallel point for securities accounts: the firm can sell your positions without contacting you first, and you don’t get to choose which ones go.

It isn’t stock margin with the dial turned up

Stock margin is a loan. You borrow cash from the broker, pay interest on the borrowed amount, and Regulation T generally caps the initial borrow at 50% of the purchase price. The SEC publication above walks through that structure.

Futures margin is a performance bond. Nothing is borrowed, no interest accrues on the posted amount, and the requirement is a slice of notional set by exchange risk models rather than a fixed statutory fraction.

The gap in the numbers is stark. At an index of 5,000, Claudia’s one contract controls $250,000 of notional against $18,000 posted — 7.2%, or roughly 13.9 to 1. Buying $250,000 of stock under Reg T takes $125,000 down. That’s 2 to 1.

The plumbing differs too. US cash equities settle T+1 after the SEC’s 2023 rule shortening the settlement cycle. Futures don’t wait for settlement dates at all; they mark to market and move cash daily through the clearing house, which is exactly why maintenance is tested continuously rather than periodically.

What a 5% day does

Five percent of 5,000 is 250 points, or $12,500 on one contract.

Claudia’s $25,000 account ends that day at $12,500 — half gone, and $3,900 below the maintenance floor, so a call on top of the loss. A $30,000 account survives it with $1,100 to spare. A $20,000 account is at $7,500 and $8,900 short.

Now run the version where she was holding two contracts on $25,000, which she couldn’t have opened but could have grown into after a good run. That same 250-point move costs $25,000. The account is at zero, and if the move overshoots, past it. Futures losses are not capped at the deposit. That sentence is doing more work than its length suggests.

When these numbers are wrong

The formula is exact. The inputs are the fragile part, and there are five specific ways they break.

Requirements change without much warning. CME raises margin when volatility rises — precisely when your cushion is already thinning. If Claudia’s initial goes to $24,000 with maintenance at $21,800, her $25,000 account drops from 172 points of room to 64, overnight, with no market move at all.

Your broker sets its own floor above the exchange’s. Retail brokers routinely require 10% to 100% more than exchange minimums, and many run a low intraday requirement that snaps back to full overnight. A $500 day-trade margin that becomes $18,000 at the close has caught a lot of people flat-footed at 4:55pm.

Gaps don’t respect your cushion. These tables assume a continuous path from entry to your call level. If the index opens 200 points lower on a Monday, an account with 172 points of room does not get filled at 172. It gets filled at whatever is there.

Spreads net down. Offsetting and calendar positions get credits under SPAN-style margining, so a long ES against a short ES in another month costs far less than two outrights. Everything above models outrights only.

Fees erode the equity being tested. Commissions, exchange fees, and NFA fees come out of the same balance the maintenance floor is measured against. On an active account that’s a few points of cushion a month, quietly.

Micro E-minis, incidentally, don’t change any of this — they’re one-tenth the size at $5 per point, so every figure divides by ten and the formula is identical.

What this doesn’t tell you

These calculations locate the margin call. They say nothing about whether the position deserves to be held, how likely a 172-point move actually is, or what size the trade should be. Probability of ruin depends on win rate, average loss, and correlation across positions — none of which appear anywhere above.

They also assume one product. A real account holding ES and NQ together gets margin offsets, so the total requirement is less than the sum of the two standalone numbers, and the cushion arithmetic has to run off the netted figure.

Tax treatment is absent too. Regulated futures contracts are taxed differently from equities in the US, and that’s an IRS question rather than a margin one.

And the $18,000/$16,400 pair is an illustration, not a current exchange level. Pull today’s numbers from CME and from your broker’s margin page, then rerun it. Three lines.

FAQ

How much money do I need to trade one E-mini S&P 500 contract?

At the illustrative $18,000 initial requirement, $18,000 opens the position. But that leaves $1,600 of cushion, which is 32 index points. Holding through a 200-point move needs $26,400; through 500 points, $41,400. What it takes to open and what it takes to survive are separate questions.

What is the difference between initial and maintenance margin?

Initial margin is the deposit required to open the position, tested once at entry. Maintenance margin is the lower balance you must stay above afterward, tested continuously. In this illustration they differ by $1,600 per contract, which is 32 index points at $50 per point.

Do I get my margin back when I close a futures position?

Yes — it’s a performance bond, not a payment. Closing the position releases the requirement, and your equity reflects the realised profit or loss. If the trade lost $2,000, the $18,000 posted comes back less that $2,000, leaving $16,000 of the original deposit.

How much can I lose on one E-mini contract?

More than you deposited. At $50 per point, a 400-point adverse move is $20,000, which exceeds the $18,000 initial margin. A 1,000-point move is $50,000 per contract. Losses aren’t bounded by the margin posted.

Why is my margin call bigger than the amount I fell short by?

Because the call restores you to the initial requirement, not to the maintenance level. Fall $400 below a $16,400 floor with $18,000 initial and the call is $2,000, because the broker is bringing you from $16,000 back to $18,000.

Does the index level change my margin requirement?

Not directly. Margin is a dollar amount per contract rather than a percentage of notional, so $18,000 covers $200,000 of exposure at 4,000 and $300,000 at 6,000. Effective leverage rises as the index rises, until the exchange resets the dollar figure — which it does periodically.

Three things to check against your own account

Your broker’s current initial and maintenance figures for the contract you trade, which may sit well above exchange minimums. Whether those figures differ intraday versus overnight, and the exact clock time of the switch. And how offsets apply if you hold more than one product, since adding standalone requirements overstates what you’ll be charged.

Then run the three lines: equity, minus maintenance, divided by dollars per point.

This article is general information, not financial advice. See our disclaimer.

More in Risk · all topics · calculators · how this was checked