What is mark price?
Three prices are on your perpetuals screen at once: the last trade, the mark, and the index. They usually sit within a few dollars of each other. In the seconds that matter — a cascade, a fat-finger sell, a thin book at 3 a.m. — they part ways, and which one your orders listen to decides whether you are still in the trade.
Last price, mark price, index price — what is each one for?
| Price | What it is | Used for |
|---|---|---|
| Last price | The most recent trade on this exchange, this contract | Your chart, market-order fills, last-price stop triggers |
| Index price | Volume-weighted spot price from several major exchanges | The anchor the contract is meant to track |
| Mark price | Index price + a decaying funding basis (exchange-specific formula) | Unrealised PnL, margin ratio, liquidation, mark-price triggers |
Formulas differ by exchange; the structure — index plus a small basis, smoothed — is common to the majors as of 2026.
Why does the exchange liquidate on mark, not last?
Because the last price on one venue can be pushed. A single large market sell into a thin book can print a trade 3% below everything else for a fraction of a second. If liquidations keyed off that print, every such wick would force-close a wave of positions at prices nobody else in the world saw — and a trader with enough size could trigger it on purpose. Anchoring liquidation to a multi-exchange index makes that manipulation expensive to the point of impossibility. It also means that during a genuine crash, when every venue falls together, the mark falls too and liquidation happens as designed.
Why did my stop trigger but I was not liquidated?
Because the two orders were listening to different prices. Your stop was set to trigger on last price; the wick printed through it, the stop became a market order and sold into the bottom of the wick. Liquidation was watching the mark, which never moved. The fix is one setting: on Binance, Bybit and OKX you can choose whether a conditional order triggers on last or mark price. For protective stops on perpetuals, mark-price triggering is usually the safer default — you want to be taken out by the market, not by one venue's hiccup. The trade-off is that a genuine local flash crash can then run past your stop before the mark catches up.
When do mark and last price separate?
During thin liquidity (weekends, early Asian hours on smaller pairs), immediately after large liquidations that empty one side of the book, on new listings before arbitrage depth arrives, and on any venue with an outage while others keep trading. Watch the gap between mark and last on your exchange; a persistent gap is a liquidity warning, and it is the moment to tighten size, not stops.
FAQ
Is unrealised PnL calculated on mark or last price? On mark price at every major perpetual exchange. That is why your displayed profit can differ slightly from what a market close would actually realise.
Can I choose which price triggers my stop-loss? Yes on the major venues: conditional orders offer last-price or mark-price triggering. Mark is usually safer for protective stops on perpetuals; last is more responsive on liquid pairs.
Can mark price be manipulated? Far harder than last price, because it is built from spot across several exchanges. Moving it would require moving the spot market itself.
Know your liquidation price before the position exists
Direction, leverage and entry in; the mark price that takes your position away out — with how far price must travel to get there.
Every key term, one roadmap
The whole slide course — ten free PDF parts, 328 pages.
Mark price is the number liquidation watches, and the funding rate is what keeps the mark and the index together. Lesson 7 — leverage and margin puts all three on one worked position, and the Bybit stop-loss how-to shows where the trigger setting lives.