A perpetual futures contract ('perp') lets you go long or short crypto with leverage and, unlike a traditional futures contract, it never expires. That raises an obvious question: without an expiry date forcing convergence with spot, what keeps the perp price anchored to the actual market price of the asset?
The Funding Rate Mechanism
The answer is the funding rate: a periodic payment exchanged directly between long and short position holders (not the exchange). If the perp trades above the index/spot price, longs pay shorts, which incentivizes selling the perp and buying spot until prices converge. If the perp trades below spot, shorts pay longs, doing the reverse.
Funding Payment = Position Notional × Funding Rate (paid every 8h on most exchanges)Mark Price vs. Last Price
Exchanges don't liquidate positions based on the last traded price, because a single thin trade could trigger an unfair cascade. Instead they use a mark price — typically the index price plus a smoothed basis — for margin and liquidation calculations. This prevents 'stop hunts' from a lone large market order on one exchange wiping out positions that were actually solvent relative to the real market.
Why Perps Dominate Crypto Derivatives
- ▸No expiry means no roll-over cost or hassle — one position can be held indefinitely.
- ▸Deep leverage (often 20x-125x) is available on major venues, though prudent traders use a fraction of that.
- ▸Funding rates themselves become a tradeable signal — persistently high positive funding often marks late-stage, over-leveraged long positioning.
If you hold a long during a period of +0.05% funding paid every 8 hours, that's roughly 0.15%/day, or ~55% annualized, quietly eaten from your position — separate from price P&L. Always check the funding rate before holding a leveraged position for more than a day or two.
Key Risks Specific to Perps
- 1.Liquidation risk scales directly with leverage — at 50x, a ~2% adverse move against you wipes the position.
- 2.Extreme funding regimes (very high positive or negative) often precede sharp mean-reversion moves as crowded positioning unwinds.
- 3.Exchange outages during high volatility can prevent you from closing a position exactly when you need to.