Perp funding rates explained

Reviewed 16 Oct 2026 against each venue's documentation · formulas quoted, not paraphrased

A perpetual future has no expiry, so nothing forces its price back to the spot price. Funding is the substitute: a periodic payment between longs and shorts, set by how far the perp trades from its index. When the perp is rich, longs pay shorts, which discourages longs and pulls the price down; when it is cheap, shorts pay longs.

Who pays whom

• Positive rate: long positions pay short positions. The perp trades above the index.
• Negative rate: short positions pay long positions. The perp trades below the index.
• The payment is position notional × rate at each funding timestamp. Nothing is charged if you are flat at that timestamp; opening one second before a settlement costs the full payment.
• On Hyperliquid, Lighter and Aster the payment is peer-to-peer: the exchange keeps none of it. Trading fees are separate.

The common formula

All three venues use the CEX-style construction popularised by BitMEX and Binance:

F = average premium index + clamp(interest rate − premium index, −0.05%, +0.05%)

• Premium index = (max(0, impact bid − index) − max(0, index − impact ask)) ÷ index, where impact prices are the average fill prices for a fixed "impact notional" on each side of the book. It measures how far a real-sized trade executes from the index.
• Interest rate stands in for the cost of carrying USD versus the coin. Hyperliquid and Aster fix it at 0.01% per 8 hours (11.6% APR, paid to shorts); Lighter sets it per market.
• Clamp keeps the interest term from dominating: it contributes at most ±0.05% when the premium is near zero. In a perfectly flat market F = interest rate = 0.01%/8h, so BTC shorts are paid a little by default.

What each venue does differently

• Hyperliquid computes the 8-hour formula every hour and pays one eighth of it each hour. Its index is a weighted median of CEX spot prices computed by validators.
• Lighter samples the premium once a minute at a random time, applies a market-specific multiplier and two clamps, and divides by eight so the premium is spread over eight hourly payments.
• Aster keeps a per-market interval of 1, 2, 4 or 8 hours and divides the 8-hour formula by 8 / N. For intervals longer than an hour it weights later premium samples more heavily. A ±2% cap per interval applies.

Converting between 1h, 4h, 8h and APR

• 8h-equivalent = rate × 8 ÷ interval hours. An hourly Hyperliquid reading of 0.00125% is 0.01% per 8h.
• Annualised = rate × 8760 ÷ interval hours. 0.01% per 8h is 10.95% APR; 0.05% per 8h is 54.75%.
• The annualised figure assumes the rate stays constant for a year. Funding on a volatile coin can swing from +0.1% to −0.1% per 8h within a day, so treat APR as a scale, not a forecast. Token pages show the 7-day average for a steadier reading.
• The calculator turns any rate, interval and holding period into dollars.

Why the same coin has different funding on different venues

• Different order books. The premium is measured on each venue's own book. A venue where leveraged longs crowd in shows a higher premium even if the index is the same.
• Different indexes. Each venue builds its index from its own set of exchanges and weights, so "spot" is not identical.
• Different parameters. Lighter's per-market multiplier and clamps, Aster's interval and ±2% cap, Hyperliquid's hourly smoothing all shape the number.
• Settlement timing. An 8h venue settles at fixed UTC hours; an hourly venue spreads the same expected cost across eight payments, so the live rate at any moment reflects a different window.
• Persistent gaps attract funding arbitrage, which tends to close them, but fees and margin on two venues set a floor on how small a gap is worth trading.
• To read the market as a whole rather than one coin, the DEX Funding Index weights every Hyperliquid and Lighter market by open interest into one annualised number, with hourly history.

Reading the tables on this site

• Every table shows the 8h-equivalent. Native rates and intervals are on token pages.
• Green is positive (longs pay), red is negative (shorts pay).
• "Max DEX gap" is highest minus lowest DEX rate for a token, annualised and gross.
• Binance and Bybit columns are reference rates from Hyperliquid's predictedFundings feed.

Sources

• Hyperliquid docs: Funding
• Lighter docs: Funding
• Aster docs: Funding Rate