Myth: a Bitunix position is liquidated when its margin hits zero. A BNB long shows where it really ends

The myth

"I put up 10% at 10x, so I can lose 10% before I'm out."

The fact

Bitunix's help centre puts it plainly: when the available margin of a position is less than the maintenance margin, the position is force-liquidated. Maintenance margin = open price x size x maintenance margin rate. So a slice of your margin is never yours to lose. It is the buffer the exchange keeps to close you out without going negative.

The image is Bitunix's live BNBUSDT perpetual page at about 10:20 AM ET: last 749.71, +0.82%, mark 749.62, index 749.25, 24h high 762.80 and low 742.27, funding 0.0126% with its countdown, the 15m chart and the order book. On the right is the order panel set to Cross 10X, the default, and at the bottom the Margin box with the two numbers this post is about: Margin Rate and Maintenance Margin. Both read zero because no position is open.

The math on 1 BNB

• Mark at 10:19 AM ET from the public API: 749.56 USDT
• At the 10x default, initial margin is 74.96 USDT
• Myth version, margin to zero: 749.56 x 0.9 = 674.60, a 10% drop
• With a maintenance rate of 0.5% (the rate Bitunix uses in its own help-centre example, for BTC at 100x, used here only as a stand-in): maintenance margin = 749.56 x 0.5% = 3.75 USDT
• Liquidation comes when the loss reaches 74.96 - 3.75 = 71.21, so near 678.35, a 9.5% drop
• Fees and funding come out of margin too and pull it a little closer. Funding is 0.0126% per 8h right now, about 0.09 USDT per BNB per settlement

Why the rate is not one number

Bitunix uses tiered maintenance rates. The bigger the position, the higher the rate and the lower the max leverage. In isolated mode each direction of each pair is tiered separately. In cross mode all of a pair's positions are added up first. The BNB rate for your size is shown behind the icon next to the pair name, not in this post.

What happens at the line

Bitunix first cancels open orders to free margin. If that is not enough, it partially closes the position to drop it into a lower tier, and only then liquidates the rest.

Same rules, other pairs

BTC, ETH, SOL and DOGE work the same way. Only the tier table and the max leverage change (BNB caps at 75x).

Have you ever checked the Margin Rate line on an open position before it got close, or only after?

Worked steps you can repeat on any Bitunix pair:

1. Take the mark price, not the last trade. Here that was 749.56 on the API against a 749.71 last.
2. Work out initial margin. Notional divided by leverage, so 74.96 USDT at 10x on 1 BNB.
3. Find the maintenance rate for your size behind the icon next to the pair name. Multiply it by notional to get maintenance margin.
4. Subtract maintenance margin from initial margin. What is left is the loss you can actually absorb, 71.21 USDT in the stand-in example.
5. Divide that loss by position size and take it off the entry. That is roughly where the line sits, before fees and funding.

Common mistakes:

• Using entry minus 1/leverage as the liquidation price. It ignores maintenance margin and puts the line too far away.
• Reading Margin Rate only after the position is in trouble. It is on the panel from the moment you open.
• Assuming a lower leverage setting lowers the maintenance rate. On Bitunix the rate follows position size and tier, so leverage only changes how much margin sits above it.
• Forgetting that cross mode adds a pair's positions together before choosing the tier, so a second position can move the first one's line.

Short FAQ

• Why did both Margin boxes read zero in the image? No position was open when it was captured.
• Will Bitunix close everything at once? Not first. It cancels open orders, then partially closes to step down a tier, and only then liquidates the rest.
• Does funding matter on a short hold? At 0.0126% per 8h it is small next to the 74.96 USDT margin, but it still comes out of the same pot.