Your chart shows last price. Your liquidation engine watches mark price. These two numbers are never the same, and at high leverage the gap between them is the difference between holding a position and losing it. This guide breaks down exactly how each price is calculated, why the gap exists, and what it means for your margin.
The Short Answer
A crypto futures contract runs on three separate price feeds: last price, index price, and mark price. Each one does a different job. Only one determines when your position gets forcibly closed.
Last price is what the chart shows — the most recent trade executed on the contract's order book. It updates every time someone buys or sells. This is what fills your orders, plots the candles, and locks in your realized profit or loss when you close a position.
Mark price is a calculated number. It anchors to a weighted spot index across multiple exchanges, then layers on a funding rate adjustment and a short-term smoothing filter. Liquidation fires on mark price, not last price. Unrealized P&L also uses mark price. It is never directly traded — it is a computed output, not a market price.
Here's the thing most guides skip: most traders ignore mark price until it costs them. Your account dashboard displays all three feeds. But the engine that decides when your position can no longer stay open watches only the mark.
| Last Price | Index Price | Mark Price | |
|---|---|---|---|
| Source | Most recent trade on this venue's order book | Volume-weighted average of spot prices across 6-15+ exchanges | Index + funding adjustment + basis smoothing (median of 3 inputs) |
| Volatility | Highest — a single large order in a thin book can spike it | Lower — anomalies on any one venue get diluted | Lowest by design — smoothing absorbs single-venue noise |
| Controls | Order fills, candle charts, realized P&L on close | Funding rate calculation, feeds into mark price formula | Unrealized P&L, liquidation trigger, mark-based stops |
| Can be manipulated? | Yes — thin books are vulnerable to wicks | Very difficult — requires moving spot prices on multiple exchanges | Extremely difficult — median of 3 derived inputs |
How Exchanges Actually Calculate Mark Price
Both Binance and Bybit use the same core formula structure. OKX uses a similar approach anchored to its own index composition. The formula:
Mark Price = Median(Price 1, Price 2, Last Contract Price)
Where:
- Price 1 = Index Price × [1 + Last Funding Rate × (Time Until Next Funding / 8 hours)]
- Price 2 = Index Price + Moving Average of the Basis over a short window
- Basis = (Best Ask + Best Bid) / 2 − Index Price
Taking the median of three values — not a simple average — means no single extreme input can push the mark price to a liquidation threshold on its own. A funding spike, a stale last price, or a brief basis expansion each get outvoted by the other two inputs.
The documented difference between exchanges is the smoothing window:
| Exchange | Spot Index Sources | Basis Smoothing Window | Deviation Cap |
|---|---|---|---|
| Binance | 15+ sources (CEX + DEX added Feb 2025) | 1 minute (60 data points) | >5% from median → capped; 5 min offline → zero weight |
| Bybit | Top 6 spot venues by 24h volume, rebalanced hourly | 2.5 minutes (150 data points) | >1% for BTC/ETH specifically |
| OKX | Multiple major spot exchanges | Similar moving average approach | Anomalous exchange data → fallback to OKX last price |
A longer smoothing window makes Bybit's mark price slightly less reactive to brief basis spikes than Binance's. The difference is small — seconds, really — but at 50x leverage, seconds matter.
Look, here's the practical implication: your liquidation can trigger at a price that never appeared on your chart. During the May 2021 BTC selloff, BTC perpetuals on some exchanges traded 2-3% below the spot index for brief periods. Without mark price protection, thousands of positions would have been incorrectly liquidated during those transient spikes. The mark price stayed close to the global spot consensus while the last price on individual venues went haywire.
When the Gap Matters — and When It Doesn't
At 2x or 5x leverage, the gap between mark and last price is background noise. The divergence is typically under 0.1%, and your liquidation price sits far enough from entry that a fraction of a percent won't change the outcome.
At 20x and above, it's a different story. A 0.5% divergence between mark and last price can be enough to trigger liquidation without a single candle printing at that level. Here's the math:
- A 20x long with 0.5% maintenance margin has roughly 4.5% of room between entry and liquidation
- A 50x long has roughly 1.5% of room
- If mark price diverges 0.5% from last price at 50x, that's one-third of your total margin buffer gone — invisible on the chart
Before opening any leveraged position, check both the last price AND the mark price on your exchange dashboard. Calculate your liquidation distance from the mark price — not the chart price. If the gap between them is wider than usual (say, over 0.3%), the market is telling you something about current order book stress. Widen your stops or reduce your size accordingly.
The gap tends to widen in three situations:
- Thin overnight trading — fewer makers means a single large order can push last price away from the spot index while mark price stays anchored
- High funding rate periods — when the funding rate is extreme (over 0.05% per 8 hours), the funding adjustment in Price 1 pulls the mark price further from the raw index
- Exchange-specific events — maintenance windows, API outages, or order book disconnections can cause last price to freeze or spike while the mark continues computing from external spot data
In March 2024, a single volatile day triggered over $800 million in liquidations within 24 hours across major exchanges, according to Coinglass data. Many of those liquidations hit at mark price levels that didn't match the candle wicks traders saw on their charts.
Practical Rules for Trading With Two Prices
Most account dashboards display all three feeds. Most traders stare at the chart and ignore the other two. Here's how to use both prices without getting caught:
Rule 1: Use last price for entries and exits. When you're reading the chart, choosing your entry level, or placing a limit order, last price is the correct reference. That's what fills your orders and plots the candles.
Rule 2: Use mark price for risk management. Once the position is open, switch your attention to mark price. Your unrealized P&L display uses it. Your liquidation price is calculated from it. Your mark-based stop-loss and take-profit triggers (if your exchange offers them) reference it.
Rule 3: Check the gap before you size up. If mark and last price are diverging by more than 0.2-0.3%, the order book is under stress. This is not the time to increase leverage. Wait for the gap to compress before adding exposure.
Rule 4: Never place your stop-loss exactly at your liquidation price. The liquidation engine uses mark price. Your stop-loss order uses last price. If the gap works against you, the liquidation can fire before your stop triggers — or vice versa. Leave at least a 0.5% buffer between your stop and your liquidation level.
Rule 5: Monitor the index price during high-volatility events. The index is the anchor for everything. If spot prices on major exchanges diverge significantly (say, one exchange shows BTC at $67,000 while others show $66,200), the index smoothing will take a few seconds to catch up. During those seconds, the mark price can be unreliable. Don't open new positions during index dislocations.
Every open position sits between two numbers: the chart price that determines how it looks, and the mark price that determines when it ends. At low leverage, the gap is invisible. At high leverage, it is part of your risk calculation — before the trade, not after.