How Perpetual Futures Work

What Are Perpetual Futures?

A perpetual futures contract — or "perp" — is a derivative that tracks the price of an underlying asset without an expiry date. Unlike a traditional futures contract that settles on a fixed date, a perpetual contract can be held indefinitely.

Perps are by far the most traded financial product in crypto. Daily volume regularly exceeds $50–100 billion — more than spot trading. Every major centralised exchange (Binance, Bybit, OKX) and a growing number of decentralised protocols (dYdX, GMX, Hyperliquid) offer them. When traders talk about "going long" or "going short" Bitcoin with leverage, they almost always mean a perpetual futures contract.

The core appeal: perps let traders express a directional view on an asset's price — up or down — with leverage, without taking custody of the underlying, without worrying about contract expiry, and with the deepest liquidity available in crypto markets.

Perps vs Traditional Futures

Traditional futures contracts have existed for centuries — commodity traders used them to lock in prices for future delivery of grain, oil, and livestock. Crypto perpetuals borrow the leverage and short-selling mechanics but discard the expiry date entirely.

The traditional futures market does have one advantage: cost predictability. You know exactly what your funding cost will be over the life of the contract (zero — you pay only at roll). With perps, funding rate payments can accumulate significantly during extended bull or bear markets, adding a hidden carry cost that long-term holders must account for.

The Funding Rate Mechanism

The funding rate is the elegantly simple mechanism that keeps perpetual futures prices tethered to spot. Without it, a perp could trade at any price relative to the underlying — making it a poor instrument for hedging or directional trading.

Every 8 hours (some exchanges: 1 hour or 4 hours), a payment occurs between long and short holders based on the difference between the perp price and the spot index price:

The funding rate is calculated using the premium index — the difference between the perp mark price and the spot index price, expressed as a percentage. Most exchanges cap funding at ±0.075% per 8-hour period (±0.225% per day). During extreme market conditions this cap is routinely hit:

Experienced traders actively monitor funding rates as a sentiment indicator. Persistently high positive funding is a contrarian warning sign: too many people are long, the carry cost is high, and a sharp correction would trigger cascading liquidations. Persistently negative funding often marks exhausted selling pressure.

Leverage & Margin

Leverage is what makes perpetual futures powerful — and dangerous. It allows a trader to control a position far larger than their deposited capital, amplifying both gains and losses by the same multiple.

When you open a leveraged position, you deposit margin as collateral. There are two critical margin thresholds:

There are two margin accounting modes that affect risk significantly:

The temptation of high leverage is seductive: 10× leverage turns a 5% market move into a 50% return. The reality is that 10× leverage also means a 10% adverse move wipes the position. Most successful perp traders use leverage between 2× and 5× — enough to meaningfully amplify returns while surviving normal market volatility. Retail traders using 50×–100× leverage are, statistically, funding the accounts of more disciplined counterparties.

Liquidations

When a position loses enough value that margin falls to the maintenance level, the exchange automatically closes (liquidates) the position — preventing the account from going into negative equity. Liquidations are the mechanism that makes leveraged trading sustainable for exchanges.

1. 1
   Price moves against the position

   A long position loses value as the asset price falls. The unrealised loss erodes the available margin. The exchange calculates margin ratio continuously in real time.

2. 2
   Margin ratio hits maintenance threshold

   When the margin ratio (available margin / position value) falls to the maintenance margin rate (typically 0.5–1%), a liquidation flag is triggered. On most exchanges, a warning is sent at a higher threshold (e.g., 2×) to give traders time to add margin.

3. 3
   Liquidation engine takes over

   The exchange's liquidation engine closes the position at the best available market price. The goal is to close quickly before the loss exceeds the deposited margin.

4. 4
   Insurance fund absorbs any deficit

   If the market moves so quickly that the position closes at a worse price than the liquidation price (a 'bankrupt' position), the shortfall is covered by the exchange's insurance fund — a pool of funds built up from partial liquidation fees on profitable liquidations.

5. 5
   Auto-deleveraging (ADL) as last resort

   If the insurance fund is depleted, the exchange uses ADL — it forcibly closes profitable positions of the most leveraged, most profitable traders against the bankrupt account. A rarely-used but important backstop.

The liquidation price for a long position at L× leverage with entry price P and maintenance margin rate m is approximately:

Liquidation Price = P × (1 − 1/L + m)

At 10× leverage with 0.5% maintenance margin: $100 × (1 − 0.10 + 0.005) = $90.50. A 9.5% drop liquidates the position. For a short, the formula mirrors: a 9.5% rise liquidates a 10× short position.

Mark Price vs Index Price

One of the most important — and frequently misunderstood — concepts in perp trading is the distinction between the price you see on the chart (last trade price), the index price (spot), and the mark price (used for liquidation).

Why not use the last trade price for liquidations? Because price manipulation. A large trader could temporarily push the perp price down with a big sell order, triggering liquidations at that artificially low price, then buy the liquidated positions at a discount. Using mark price — which is a smoothed, multi-source average — makes this attack expensive and difficult.

In practice: if the perp market temporarily spikes or crashes due to a large order, your unrealised PnL and liquidation risk are calculated on mark price, not last price. You will not be liquidated by a momentary price wick that immediately recovers — as long as mark price stays above your liquidation threshold.

CEX vs DEX Perpetuals

Perpetual futures are available on both centralised exchanges (CEX) — where the exchange holds your funds and matches orders off-chain — and decentralised protocols (DEX) — where smart contracts handle custody, margin, and liquidation on-chain.

The key tradeoff is custody vs liquidity. On a CEX, your funds are held by the exchange — you bear counterparty risk (exchange insolvency, hack, withdrawal freeze). In return you get the deepest liquidity, fastest execution, and the widest range of instruments. On a DEX, you control your own keys — but you typically face thinner liquidity, higher fees, and smart contract risk.

The DEX perp market has grown dramatically since 2022. Hyperliquid in particular demonstrated that on-chain order books can achieve near-CEX-quality execution, with sub-second block times on its native L1. The next generation of DEX perps will likely close the remaining liquidity gap with CEXs.

Risks

Perpetual futures are among the riskiest instruments available to retail traders. The combination of leverage, funding costs, and 24/7 markets creates a uniquely hostile environment for the underprepared.

Why Perps Dominate Crypto

Perpetual futures did not exist before 2016. Within a decade they became the dominant trading instrument in the entire crypto market. Understanding why reveals something important about what traders actually want.

The funding mechanism elegantly solves the "what happens without expiry?" problem. Traditional futures need an expiry date because that is what forces price convergence to spot — delivery at expiry. Perpetuals replace delivery with a continuous financial incentive: if the price diverges from spot, one side gets paid to take the correcting trade. The market self-regulates in real time rather than once per quarter.

For the crypto market specifically, perps solved a critical problem: in 2016, getting short exposure to Bitcoin was complex, expensive, and required significant trust in margin lending counterparties. BitMEX's introduction of the perpetual swap made shorting as simple as clicking a button — democratising the full range of trading strategies and, in doing so, improving price discovery and market efficiency enormously.