Funding Rate Calculation

The funding rate consists of two parts: Interest Rate and Average Premium Index (P).

 

Bybit calculates the Interest Rate (I) and the Average Premium Index (P) every minute by performing an N*-Hour Time-Weighted-Average-Price (TWAP) over the series of minute rates. The closer to the funding fee settlement time, the greater the coefficient of the premium index.

 

Taking an 8-hour funding interval as an example, the Average Premium Index (P) is calculated using the formula: (Premium Index _1 * 1 + Premium Index _2 * 2 +... + Premium Index _480 * 480)/(1 + 2 +... + 480).

 

Each hour corresponds to 60-minute intervals. If the funding interval is every 4 hours, corresponding to 240 intervals (4 * 60), then the coefficients would be 1, 2, ..., 240, forming an arithmetic progression starting from 1 with a common difference of 1.

 

The Funding Rate is next calculated with the N*-Hour Interest Rate component and the N*-Hour premium/discount component. A +/−0.05% dampener is added.

*N = Funding Time interval. Suppose funding occurs once every 8 hours, N = 8. And if funding occurs once per hour, N = 1.

 

Funding Rate (F) = Average Premium Index (P) + clamp (Interest Rate (I) − Average  Premium Index (P), 0.05%, −0.05%)
 

Hence, if (I − P) is within +/−0.05%, then F = P + (I − P) = I. In other words, the funding rate will equal the Interest Rate.

 

This calculated funding rate is then applied to a trader’s position value to determine the funding fee to be paid or received at the funding timestamp.

 

 

 

Interest Rate (I)

Formula

Interest Rate (I) = Price Interest Rate Index − Base Rate Index/Fund Rate Interval

• Interest Quote Index = The interest rate for borrowing the quoted currency

• Interest Base Index = The interest rate for borrowing the base currency

• Funding Interval = 24/Funding Time interval

 

Exception: For the USDCUSDT contract, the interest rate (I) will default at 0.000001% as both the base token and quoted token are stablecoins.

 

Let’s take BTCUSD as an example.

 

Every contract traded on Bybit comprises a base currency, such as BTC, and a quoted currency, such as USD. The interest rate is a function of the difference in interest rates between these two currencies. In this case, this is the difference between the borrowing costs of BTC and USD.

 

Tip: You can view the BTC lending rate under the Contract Details.

 

 

Factors

Funding time interval: 3 = 24/8 (assuming funding time intervals occur every 8 hours)

Interest Quote Index = 0.06%

Interest Base Index = 0.03%

This is based on the following calculation:
Interest Rate = (0.06% − 0.03%)/3 = 0.01%

 

 

 

 

Premium Index (P)

Perpetual contracts may trade at either a premium or discount from the mark price. In this situation, a premium index will be used to raise or lower the next funding rate to align with the level of the contract trade.

 

Tip: You can view the history of the premium index in Premium Index under the Contract Details.

 

 

Formula

Premium Index (P) = [Max (0, Impact Bid Price − Index Price) − Max (0, Index Price − Impact Ask Price)]/Index Price

 

* Impact Bid Price = The average fill price to execute the Impact Margin Notional on the Bid side

* Impact Ask Price = The average fill price to execute the Impact Margin Notional on the Ask side

 

 

Impact Margin Notional (IMN) is the notion available to trade with a certain amount of margin. It’s used to determine how deep the order book is and to measure the Impact Bid or Ask Price.

 

The IMN is configured in USDT value and can be found here. To obtain the corresponding base coin quantity from the order book, the formula is as follows:

 

Base Coin Quantity =  Impact margin national / [(bid1+ask1)/2]

 

 

 

 

 

 

Funding Rate Limit

During periods of significant market volatility, Bybit may temporarily adjust the upper and lower limits of the Funding Rate to encourage the Perpetual Contract's price to return to a reasonable range. 

 

Under normal circumstances, the funding rate limit = ± Min ((IMR-MMR) x 0.75, MMR), where IMR and MMR represent the initial margin rate and maintenance margin rate requirements of the lowest risk limit tier for each symbol. However, when there is a significant price difference between the futures market and the spot market, we will adjust the coefficient of 0.75, within a range from 0.75 to 1.

 

To view the updated Funding Rate Limit, please visit here.