What is perpetual swap premium index? How is funding calculated?

Premium Index Definition and Function

1. The premium index is a real-time metric that quantifies the deviation between the perpetual swap price and the underlying index price.

2. It is computed as the weighted average of the mid-price spread across multiple top-tier spot exchanges, normalized against the index price.

3. A positive premium index indicates the perpetual contract is trading above the spot index, signaling bullish sentiment or excessive long leverage.

4. A negative premium index reflects persistent discounting, often associated with dominant short positioning or forced liquidations in bearish momentum.

5. Exchanges like Binance and Bybit publish this value transparently on their contract pages to inform traders about current market skew.

Funding Rate Calculation Mechanics

1. Funding rate equals the sum of the interest rate component and the premium index multiplied by 0.01.

2. The interest rate component remains fixed at 0.01% per 8-hour interval for most major pairs, representing the theoretical cost of borrowing the quote asset.

3. The premium index term introduces dynamic adjustment: when the index exceeds +0.005, funding turns positive and longs pay shorts; when it falls below −0.005, funding flips negative and shorts pay longs.

4. Settlement occurs precisely every 8 hours — at 00:00, 08:00, and 16:00 UTC — regardless of market volatility or liquidity conditions.

5. Traders can observe live funding values in the “Contract Info” panel or via the “Funding History” chart, where spikes often coincide with large liquidation cascades.

Open Interest and Its Relationship to Premium

1. Open interest represents the total number of active long and short positions held across all accounts on a given exchange.

2. Sustained divergence between open interest growth and traded volume may indicate accumulation rather than speculative turnover.

3. When open interest rises alongside a sharply positive premium index, it suggests leveraged longs are entering without corresponding hedging activity.

4. Abrupt drops in open interest during negative funding periods frequently reflect mass liquidations rather than voluntary position closures.

5. Some derivatives platforms have been found to report implausible open interest figures, especially during high-volatility intervals, raising questions about data integrity.

Arbitrage Opportunities Around Funding Events

1. Traders monitor the time until next funding settlement to anticipate directional pressure from large open interest imbalances.

2. Cross-exchange basis trades emerge when one platform shows significantly higher premium than another for the same underlying pair.

3. Carry strategies involve holding long positions during extended negative funding regimes while financing costs remain below expected spot appreciation.

4. Short-term reversal plays target the moment just before funding clock resets, exploiting overextended positions that rush to close ahead of payment obligations.

5. Automated bots scan for anomalies such as inverted funding signs across correlated assets — for example, BTCUSDT showing +0.02% while ETHUSDT shows −0.01% — indicating fragmented market consensus.

Frequently Asked Questions

Q1. Can funding rate go above +0.75% or below −0.75%?Yes. While most exchanges cap funding at ±0.75% per 8-hour period, extreme market dislocations — such as flash crashes or exchange outages — have triggered uncapped rates exceeding ±1.5% on isolated occasions.

Q2. Is the premium index affected by order book depth?No. The premium index relies solely on executed trade prices from selected spot venues, not bid-ask spreads or resting limit orders.

Q3. Do all perpetual swaps use the same index calculation method?No. Binance uses a time-weighted average of five spot exchanges; Bybit incorporates six with different weighting coefficients; OKX applies a median filter to exclude outlier feeds.

Q4. How do exchanges handle funding during maintenance downtime?Funding settlements proceed automatically even during scheduled maintenance. Missed payments due to wallet unavailability are applied retroactively upon restoration without penalty or interest accrual.