Mark Price vs Index Price vs Last Price in Crypto Futures
Mark price, index price and last price are the three prices on a perpetual futures contract. Learn what each measures and why liquidations use the mark price.
Updated
The index price is an average spot price from several exchanges, the mark price is a fair-value price derived from it and used for PnL and liquidations, and the last price is the price of the most recent trade on the contract. Every perpetual futures contract has all three. Knowing which one drives which calculation helps you avoid surprise liquidations and misread charts.
Key takeaways
- Index price: weighted average of spot prices across several exchanges.
- Mark price: fair value used for unrealized PnL and liquidations.
- Last price: latest trade on the contract; what most charts show.
- Liquidations use mark price, so a brief wick in last price usually does not liquidate you.
- The gap between the perp price and the index feeds into the funding rate.
The three prices compared
| Index price | Mark price | Last price | |
|---|---|---|---|
| What it measures | Underlying spot market | Fair value of the contract | Latest actual trade |
| Source | Spot prices from several exchanges | Index plus a smoothed premium or median of inputs | The contract's own order book |
| Used for | Funding premium, input to mark price | Unrealized PnL, margin ratio, liquidation | Charts, order fills, some stop triggers |
| Sensitivity to wicks | Low | Low | High |
How the index price is built
Exchanges take spot prices for the asset from a set of major venues and combine them, usually with weights based on volume or reliability. Outlier prices are often excluded or capped. Because the index draws on many markets, one exchange having a flash crash does not move it much.
Index construction differs by exchange: the list of source venues, the weights and the outlier rules are all venue-specific.
How the mark price is built
The mark price aims to reflect fair value without the noise of single trades. Common approaches include:
- Index plus a moving average of the premium: the index price, adjusted by a smoothed measure of how far the perp has traded above or below it.
- Median of several inputs: for example, the median of the index-based price, a premium-adjusted price and the last price.
Either way, the mark price stays close to the index but still reflects a persistent premium or discount on the perp.
Worked example: a wick that does not liquidate
You hold a BTC long with a liquidation price of $48,500. A large market sell hits a thin order book:
| Price | Before the wick | During the wick (a few seconds) |
|---|---|---|
| Index price | $50,120 | $50,100 |
| Mark price | $50,100 | $50,080 |
| Last price | $50,110 | $48,000 |
The last price briefly falls $500 below your liquidation level ($48,500 − $48,000), but the mark price stays $1,580 above it ($50,080 − $48,500). Your position is not liquidated. If liquidation used the last price, it would have been closed.
A stop-loss set to trigger on the last price at $49,000 would have fired during this wick, filling near the bottom. The same stop on the mark price would not have triggered.
Where the perp basis comes from
The difference between the perp's traded price and the index is the perp premium, a form of basis. Exchanges measure it over each funding interval:
- Perp above index: funding tends to be positive, and longs pay shorts.
- Perp below index: funding tends to be negative, and shorts pay longs.
That link is what keeps a perp close to spot without an expiry date.
Practical tips
- Estimate liquidation against the mark price, not the chart price. The liquidation price calculator shows how leverage and maintenance margin set the level.
- Choose your stop trigger deliberately: last price reacts faster, mark price ignores short wicks.
- Watch the mark-last gap in thin markets. A large gap means the order book is under stress.
- Compare venues: the same coin can have different mark prices on different exchanges because their index sources differ.
For more on how liquidation works once the mark price hits your level, see what is liquidation.
Frequently asked questions
- What is the mark price in crypto futures?
- The mark price is an exchange's estimate of a futures contract's fair value, built from the index price and other inputs. It is used to calculate unrealized profit and loss and to decide when positions are liquidated.
- What is the index price?
- The index price is a weighted average of the spot price of an asset across several major exchanges. It represents the underlying market price and is harder to manipulate than the price on any single venue.
- What is the last price?
- The last price is the price of the most recent trade on that specific contract. It is what most charts show, and it can spike briefly on thin liquidity or large orders.
- Why are liquidations based on the mark price instead of the last price?
- Using the mark price protects traders from being liquidated by a brief wick or a manipulated trade on one exchange. A position is only liquidated when the broader fair price moves against it.
- Can I choose which price triggers my stop-loss?
- On many exchanges, yes. Stop and take-profit orders can often be set to trigger on either the last price or the mark price, while liquidations always use the mark price.