What Is Cross Margin? Shared Collateral Mode Explained
Cross margin is a margin mode in perpetual futures trading where your entire account balance serves as collateral for all open positions. Rather than assigning a fixed amount of margin to each trade individually, cross margin pools your available USDC balance so that every position can draw on the same funds. This mechanism makes it harder for any single position to be liquidated, but it also means your whole account is at stake if the market moves sharply against you.
How Cross Margin Works
When you open a position in cross margin mode, the exchange does not ring-fence a specific portion of your balance for that trade. Instead, it treats your free balance as a shared buffer that any position can tap into when needed.
Here is what happens step by step:
- You deposit 2,000 USDC into your Perpmate trading account.
- You open a 10x long on BTC worth 10,000 USDC, requiring 1,000 USDC initial margin.
- You have 1,000 USDC remaining as free balance.
- If BTC drops and your long position shows an unrealized loss of 800 USDC, the exchange automatically uses part of your free balance to keep the position alive.
- Your effective margin for the BTC position is now 1,800 USDC (1,000 original + 800 drawn from free balance), pushing your liquidation price further away.
Without cross margin, that same 800 USDC loss on a 1,000 USDC isolated position would have already triggered liquidation.
Cross Margin vs Isolated Margin
Understanding the difference between cross and isolated margin is one of the most important decisions you make before placing a trade.
| Feature | Cross Margin | Isolated Margin |
|---|---|---|
| Collateral scope | Entire account balance | Fixed amount per position |
| Liquidation risk per trade | Lower (more buffer) | Higher (less buffer) |
| Account-wide risk | Higher (whole balance exposed) | Lower (losses capped per trade) |
| Capital efficiency | More efficient | Less efficient |
| Best suited for | Hedged portfolios, correlated pairs | Speculative one-off trades |
When Cross Margin Protects You
Suppose you hold two positions simultaneously:
- Long ETH at 10x, position size 5,000 USDC
- Short BTC at 10x, position size 5,000 USDC
If BTC and ETH move in the same direction, one position profits while the other loses. Under cross margin, the winning position's unrealized gain offsets the losing position's margin draw, keeping both positions healthy without additional deposits.
When Cross Margin Hurts You
Now imagine you hold two long positions in a market-wide crash:
- Long BTC at 20x, position size 20,000 USDC
- Long SOL at 20x, position size 10,000 USDC
Both are losing. BTC drops 3% and SOL drops 8%. The combined unrealized loss eats through your free balance, and the exchange liquidates both positions once your account equity falls below the maintenance margin threshold. In isolated margin mode, the SOL position would have been liquidated alone, leaving your BTC position and remaining balance untouched.
Practical Example on Perpmate
Consider a trader with 5,000 USDC in their Perpmate account using cross margin mode:
| Action | Position Size | Leverage | Margin Used | Free Balance |
|---|---|---|---|---|
| Deposit | -- | -- | 0 USDC | 5,000 USDC |
| Open long BTC | 20,000 USDC | 10x | 2,000 USDC | 3,000 USDC |
| Open long ETH | 10,000 USDC | 10x | 1,000 USDC | 2,000 USDC |
| BTC drops 5% (unrealized -1,000 USDC) | -- | -- | 3,000 USDC effective | 1,000 USDC |
| ETH rises 3% (unrealized +300 USDC) | -- | -- | -- | 1,300 USDC effective |
The 2,000 USDC free balance and the ETH unrealized gain combine to cushion the BTC loss. The trader avoids liquidation even though BTC alone moved 5% against a 10x position, which under isolated margin would have consumed half the dedicated margin.
Managing Risk in Cross Margin Mode
Because your entire balance is on the line, risk management is even more critical in cross margin mode:
- Use stop-losses on every position: A stop-loss (TL) closes your trade before the loss consumes your account. This is non-negotiable in cross margin.
- Keep leverage moderate: Even though cross margin offers more breathing room, using 20x or 40x across multiple positions can wipe your account in a single volatile candle.
- Monitor total exposure: Add up the notional value of all your open positions and compare it to your account balance. If your combined exposure is 10 or more times your balance, consider reducing.
- Separate speculative capital: If you want to take a high-risk trade, consider switching that specific position to isolated margin so it cannot drain funds from your other positions.
- Track funding costs: Funding rate payments are debited from your shared balance, so holding multiple large positions in cross margin amplifies funding costs over time.
Who Should Use Cross Margin?
Cross margin is generally preferred by:
- Hedged traders who hold offsetting long and short positions across correlated assets
- Market makers who need capital efficiency across many simultaneous orders
- Experienced portfolio traders who actively monitor total account exposure
If you are new to perpetual futures, starting with isolated margin is the safer choice until you are comfortable managing account-wide risk.
For a complete comparison of cross vs. isolated margin with worked examples, see Cross Margining in Crypto.
Related Terms
- Margin: The collateral backing your leveraged positions
- Isolated Margin: The alternative mode that caps risk per position
- Liquidation Price: The price at which your margin is depleted
- Leverage: The multiplier that determines position size relative to margin
- Funding Rate: Periodic payments that affect your shared balance