Margin tells you how many contracts you’re allowed to hold. It says almost nothing about how many you should. On a funded account those are two completely different questions, and confusing them is one of the fastest ways to blow an evaluation.
Initial vs maintenance margin
Exchanges set two numbers for every futures contract, and they’re often conflated:
- Initial margin is the amount your account must have available to open a position. It’s the exchange’s good-faith deposit, not the cost of the contract.
- Maintenance margin is the lower amount you must keep in the account to hold the position open. Drop below it and you face a margin call or a forced liquidation.
Both are set by the exchange (via SPAN) and adjusted when volatility rises — margins get raised into events like FOMC precisely because the risk goes up. Neither number is your risk on the trade. They’re collateral requirements, and treating “I have enough margin for ten contracts” as permission to trade ten contracts is exactly backwards.
Day-trade margin and intraday buying power
Here’s where beginners get the most dangerous impression of leverage. Brokers and prop firms offer a day-trade margin far below the exchange’s overnight initial margin — sometimes a small fraction of it — as long as you close before the session ends. Hold past the close and the position reverts to full overnight margin.
| Margin type | When it applies | Set by | Relative size |
|---|---|---|---|
| Initial | Opening a position | Exchange (broker can raise) | Higher |
| Maintenance | Holding a position | Exchange (broker can raise) | Just below initial |
| Day-trade / intraday | Flat by session close | Broker | Much lower |
That intraday buying power can make it look like you can trade a huge position on a tiny balance. You can, technically. But day-trade margin is a broker courtesy, not a risk budget. Two consequences matter for funded traders:
- It’s revocable. Firms cut day-trade margin around news or raise it without much notice, and a position sized to the old number can suddenly be under-collateralized.
- It amplifies mistakes. Low day-trade margin is the mechanism by which a trader controls far more notional than their drawdown can survive.
Notional value and true leverage per contract
The number that actually describes your exposure is notional value — the full dollar value of what the contract controls, not the margin you posted. Notional is the futures multiplier times the price.
Consider the gap. An ES contract at a $50 multiplier represents roughly a quarter-million dollars of index exposure on a few thousand dollars of day-trade margin. Your true leverage is notional ÷ the capital genuinely backing the trade — often an order of magnitude higher than the “leverage” implied by margin alone. A one-percent move against a heavily notional position isn’t a one-percent account move; it can be a large multiple of your margin.
The takeaway: size by what the contract controls, not by what it costs to open. When you think in notional, the temptation to stack contracts because “the margin’s cheap” evaporates.
How prop buying power differs from a retail broker
A funded account layers a second rulebook on top of the exchange’s. Your prop firm sets its own maximum contract limits, daily loss limits and drawdown — and those are usually the binding constraints, not margin.
The mental model that keeps funded traders solvent:
- The exchange decides what you can collateralize.
- The firm decides the most you’re permitted to trade and lose.
- You decide, well inside both, what your strategy actually justifies.
Firms also scale contract limits by account size and phase, and they can change them. Never build a strategy that only works at the firm’s maximum size — confirm the current limits with your firm, because they vary by program and change over time. Programs like Topstep publish contract and loss limits per plan; treat those as ceilings you rarely approach, not targets.
Why margin isn’t your real risk limit — drawdown is
Here’s the whole point in one line: margin governs whether a trade can be opened; drawdown governs whether your account survives. You can be nowhere near a margin call and still breach a trailing drawdown on a single oversized loser. The exchange never stops you at your firm’s line — that’s your job.
So size to your dollar risk per trade and your remaining drawdown cushion, then check that margin allows it — in that order, never the reverse. Fix the dollars you’ll lose if the stop hits, let the stop distance set the contract count with a position size calculator, and confirm the result sits well inside your floor — ideally with room for several consecutive losses, not just one. Understanding how that floor moves is essential reading — see how trailing drawdown works.
This is where enforcement beats intention. Shibiki can push a hard max-loss limit down to the broker, so no amount of available margin can carry you past your daily line on a fast move — the limit holds even when discipline slips. Its live edge health, tracked with a Wilson confidence interval, keeps you from scaling size up on a strategy the sample hasn’t actually proven yet. Run several accounts and the same ceiling copies across every one.
Related: Position size calculator · Trailing drawdown, explained · Topstep