BloFin mark vs last on BTC, advanced: three prices on one screen, and only one of them can liquidate you

A) What each number does on BloFin

Index is a weighted average of spot prices from several large exchanges. It anchors the contract and sets the allowed range for limit orders. Mark is the fair-value estimate built from index plus a funding basis. BloFin uses it for liquidation, margin ratio and unrealized PnL. Last is the most recent fill on the BloFin book. It drives execution, realized PnL and any TP/SL you set to trigger on last.

BloFin lets you pick mark, index or last as the trigger for TP/SL. At this tier, that choice is the whole game.

B) Reading the Nov 3 snapshot

Last minus mark: 77,827 - 77,833.1 = -6.1. Mark minus index: 77,833.1 - 77,858.7 = -25.6, about -0.033%. Last minus index: -31.7.

So the perp traded at a small discount to spot, and mark sat between the two, closer to last. The 24h range on last ran from 76,349.9 to 77,918, a 1,568.1 swing, about 2.04% of the 76,770 open. The three-price gap is the part that changes under stress.

C) Worked example: the fill that shows red instantly

Buy 0.1 BTC at market. You take the ask, 77,836.9 at the snapshot. Mark was 77,833.1. Unrealized PnL right after the fill = 0.1 x (77,833.1 - 77,836.9) = -0.38 USDT. Short 0.1 BTC at the bid, 77,836.6, and the same math reads +0.35 USDT. Nothing was lost. Unrealized PnL is marked to mark, not to your fill, so it starts from the bid/ask-to-mark gap (fees not included).

D) Worked example: the wick only one stop sees (illustrative)

Same long, 0.1 BTC from 77,827, stop at 77,000. Now imagine a thin moment where last prints 76,900 for two seconds while mark, smoothed against the index, only dips to 77,700. Those two prices are illustrative, not from the snapshot.

Stop on last: it triggers, fills near 76,900 and books 0.1 x (77,827 - 76,900) = 92.7 USDT of loss before fees. Price recovers and you are flat. Stop on mark: mark never reached 77,000, so the stop stays dormant and the position survives the wick.

Now flip it. In a real, broad sell-off the index falls on every venue. Mark follows the index, so a mark stop fires too, just a moment later than a last stop would. Mark triggers trade wick protection for a little lag.

E) Where liquidation actually sits

BloFin starts liquidation when mark reaches your liquidation price, cancels eligible open orders to free margin and hands the position to the liquidation engine. Two consequences:

1. Measure your buffer from mark. If your panel shows an estimated liquidation at 74,000 (hypothetical), the distance is 77,833.1 - 74,000 = 3,833.1, about 4.92% of mark.
2. A last-price stop placed a hair above liquidation can lose the race. If the perp is at a premium that collapses, mark can fall through your liquidation line while last is still above your stop.

F) Common mistakes

• Watching the default candle chart (last) and assuming you are safe because the candle never touched your liquidation line.
• Leaving every stop on its default trigger without checking which price it uses.
• Reading a small red PnL after a market fill as a slippage loss.
• Putting a stop so close to liquidation that a mark move gets there first.
• Forgetting that the basis can flip from discount to premium during the day, which changes which price moves first.

G) Short FAQ

Q: Why was I liquidated when the chart never reached my price? A: The chart shows last. Liquidation is checked on mark.

Q: Should every stop use mark? A: Not always. Mark helps on thin pairs and wicky sessions. Last can suit fast scalps where you want out exactly when the book trades there.

Q: Does index ever matter for me? A: It caps how far a limit order can sit from the market and it anchors mark, so a big spot move shows up in your risk even if the perp book is quiet.

Run the same three-price check on BTC, ETH, SOL, XRP and DOGE. At the same BloFin snapshot, ETH-USDT read last 2,289.26 vs mark 2,289.38, while SOL-USDT read last 93.6 vs mark 93.51, so SOL had last above mark while BTC and ETH had last below it.

Rule to keep: your liquidation lives on mark, so the trigger on your stop should be a deliberate choice, never a default.