Myth vs fact on MEXC perps: your liquidation is not triggered by the last traded price. A perpetual futures 101, read off one BTCUSDT header

A perpetual future is a futures contract with no expiry date. On MEXC it stays open until you close it or it gets liquidated, and a regular funding payment between longs and shorts keeps its price anchored to spot. On the USDT-M side, margin, fees and profit and loss are all counted in USDT, so a 40 USDT gain reads as roughly 40 dollars.

That short definition hides four prices and a clock. The attached image, taken from MEXC's own help article on futures liquidation, shows all of them in one row.

What the image shows: the MEXC web futures page for BTCUSDT Perpetual with a 400x tag. The header reads a last price of 81,918.4, Index Price 81,962.4 and Fair Price 81,930.0 (MEXC boxed those two in red), Funding Rate / Countdown +0.0050% / 02:28:05, 24h high 83,951.6 and 24h low 79,903.9. Below it sits a 15m candle chart dated 2025/03/14 with the price-source dropdown set to Last Price (also boxed by MEXC), and the order book on the right. These are March 2025 numbers from MEXC's capture, not live quotes.

Read the row left to right:

1. "Perpetual" and the 400x tag

No settlement date. MEXC lists USDT-M leverage from 1x to 500x; the cap is set per pair and changes over time, and this BTCUSDT capture shows 400x. Leverage only decides how much margin you post: position value / leverage. It does not set your maintenance margin rate. MEXC sizes that by position size through risk-limit tiers (BTC has 6), so a bigger position needs a higher rate whatever leverage you pick.

1. Last price, 81,918.4

The most recent trade on this contract. It is what your orders fill against and what the chart shows by default. It does not decide liquidation.

1. Index Price, 81,962.4

A weighted average of prices from major exchanges. MEXC says its BTC index references Bybit, HTX and MEXC.

1. Fair Price, 81,930.0

This is MEXC's mark price. It drives unrealized PnL and the liquidation trigger, never realized PnL. MEXC's formula:

Fair Price = median of (funding rate premium, mid-price basis fair price, last price) funding rate premium = index x (1 + latest funding rate x hours to next settlement / hours in the cycle)

You can check it against the screenshot. Assuming the standard 8 hour cycle, the 02:28:05 countdown is about 2.47 hours: 81,962.4 x (1 + 0.00005 x 2.47 / 8) = about 81,963.7

The last price is 81,918.4. A median of three numbers is the one in the middle, and 81,930.0 is neither of those two, so the median here was the third input: the basis price (index plus a moving average of order-book mid minus index). Fair Price sat 32.4 below the index and 11.6 above the last trade.

That 11.6 gap is why a fresh position can show unrealized PnL the moment it fills. A 0.01 BTC long filled at 81,918.4 and marked at 81,930.0 shows about +0.12 USDT straight away (11.6 x 0.01 = 0.116). MEXC calls this normal; nothing is gained or lost until you close.

1. Funding Rate / Countdown, +0.0050% / 02:28:05

Positive rate: longs pay shorts. Negative rate: shorts pay longs. MEXC takes no cut; the money moves between traders.

Funding fee = position value x funding rate, where position value = size x Fair Price.

Settlement is generally every 8 hours at 00:00, 08:00 and 16:00 UTC (8 PM, 4 AM and noon ET while daylight time lasts), but some pairs run a different cycle, so go by the countdown on the pair. You only pay or receive if you hold a position at settlement, and MEXC warns that orders within 15 seconds either side of it may or may not be counted.

At the screenshot's rate, a 0.01 BTC long marked at 81,930.0 is worth 819.30 USDT and would pay 819.30 x 0.00005 = about 0.041 USDT at that settlement.

1. Liquidation, which is not on the header at all

MEXC watches a margin rate: margin rate = (maintenance margin + liquidation fee) / (position margin + unrealized PnL)

At 100% the position is liquidated, and the trigger is Fair Price reaching your liquidation price, not a last-price wick. For an isolated long, leaving out the liquidation fee as MEXC's own examples do: liquidation price = (maintenance margin - position margin + entry x quantity) / quantity

Worked example (made-up round numbers, not live prices or tiers): a 1 ETH long on the ETHUSDT perpetual at 4,000 USDT with 20x, isolated, assuming a 0.5% maintenance rate.

• Position value: 1 x 4,000 = 4,000 USDT
• Margin at 20x: 4,000 / 20 = 200 USDT
• Maintenance margin: 4,000 x 0.005 = 20 USDT
• Liquidation price: (20 - 200 + 4,000) / 1 = 3,820 USDT, a 4.5% drop
• One funding settlement at an assumed +0.01% with Fair Price at 4,000: 4,000 x 0.0001 = 0.40 USDT paid by the long, or 1.20 USDT across three settlements in a day
• Opening as a taker at the 0.02% rate MEXC's USDT-M guide lists (it notes rates can vary by region): 4,000 x 0.0002 = 0.80 USDT

Same trade at 40x: margin drops to 100 USDT, so liquidation moves to (20 - 100 + 4,000) / 1 = 3,920 USDT, only 2% away.

When liquidation does hit, the engine takes the position over at the bankruptcy price, the level where the margin would be fully gone. That price never prints on the chart because it skips the matching engine. MEXC's own SOLUSDT example: a 100x long from 196.09 was liquidated when Fair Price reached 194.59 and was taken over at 194.14. Any margin left after the takeover goes to the insurance fund.

Quick FAQ

Q: Can I hold a long and a short on the same pair? A: Yes. MEXC supports two-way positions, with separate leverage for each side.

Q: Can funding come out of my position margin? A: Only if available margin runs short. Then it is taken from position margin and the liquidation price moves closer to Fair Price.

Q: Can I switch a position back from cross to isolated? A: Not currently, per MEXC. Isolated to cross is allowed.

Q: Does any of this change on other coins? A: The formulas are the same on ETHUSDT, SOLUSDT, XRPUSDT and DOGEUSDT. Max leverage, risk tiers and the funding cycle are set per pair under Information on the futures page.

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