Funding rate in perpetual contract trading: what it is and how it works

Funding rate is a key mechanism in the perpetual contract market used to maintain the balance between contract prices and spot prices. For users trading on the derivatives trading page, understanding the funding rate is crucial because it directly impacts your trading costs and profits. Unlike traditional futures, the funding rate ensures that perpetual contract prices do not deviate excessively from the actual market price through periodic funding exchanges.

How the Funding Rate Updates in Real Time

When trading derivatives, the funding rate is continuously adjusted based on real-time market conditions, with calculations and updates every minute. This rate fluctuates dynamically throughout the entire funding cycle before it takes effect. For example, in an 8-hour funding cycle, the process is as follows:

• From UTC midnight to 8 a.m., the system calculates the funding rate during this period, which then takes effect and is paid at 8 a.m.
• From 8 a.m. to 4 p.m., the calculated rate becomes effective and the corresponding funds are transferred at 4 p.m.

This real-time calculation method ensures that the funding rate accurately reflects the latest market supply and demand conditions.

The Funding Rate Comprises Two Main Components

The calculation of the funding rate includes two core parts: Interest Rate (I) and Premium Index (P). The Bybit platform recalculates these two components every minute, using a time-weighted average price (TWAP) method that processes multiple minute-level data points over a certain period. As the funding time approaches, the weight of the premium index increases, providing a more accurate reflection of the latest market conditions.

The formula is: Funding Rate (F) = Limit[ P + Limit( I − P, 0.05%, -0.05%), upper limit, lower limit]

Meaning and Calculation of the Interest Rate Component

The interest rate component is calculated using a fixed formula: Interest (I) = 0.03% / (24 / Funding Cycle)

For example, for BTCUSD perpetual contracts, the fixed daily interest rate is 0.03%. In an 8-hour funding cycle, this equates to approximately 0.01% per cycle. Note that for certain trading pairs (such as USDCUSDT or ETHBTCUSDT), the interest rate component is set to zero by default.

How the Premium Index Affects the Funding Rate

Perpetual contracts may trade at a premium or discount relative to the spot market price. To guide the contract price back to a reasonable range, the system adjusts the next funding rate cycle based on the degree of premium or discount. You can view historical data in the premium index section of the contract info page.

The premium index is calculated as: Premium Index (P) = [max(0, Buyer Price Impact − Index Price) − max(0, Index Price − Seller Price Impact)] / Index Price

Key concepts involved:

• Seller Price Impact refers to the average transaction price needed to execute a specified nominal margin (seller side).
• Buyer Price Impact refers to the average transaction price needed to execute a specified nominal margin (buyer side).

The system applies a time-weighted average algorithm to the premium index, incorporating all values from the previous calculation cycle to the current moment, with more recent data weighted more heavily.

Limits on the Funding Rate

The funding rate is not unlimited; the system sets upper and lower bounds to prevent extreme values. Under normal market conditions:

• Upper Limit = minimum[(Initial Margin Rate - Maintenance Margin Rate) × 0.75, Maintenance Margin Rate]
• Lower Limit = -minimum[(Initial Margin Rate - Maintenance Margin Rate) × 0.75, Maintenance Margin Rate]

Here, the Initial Margin Rate (IMR) and Maintenance Margin Rate (MMR) refer to the minimum risk requirements for the specific trading pair.

In times of significant market volatility, Bybit may temporarily adjust these limits by changing the 0.75 coefficient (adjusted between 0.5 and 1.0) to encourage the contract price to return to a rational range. To learn about the latest funding rate limit settings, you can visit the official announcement page.

Funding Rate Rules in Pre-Market Perpetual Contracts

Before perpetual contracts officially go live, during the pre-market phase, the funding rate calculation differs and falls into two scenarios:

1. During Market Maker Auctions: The funding rate is fixed at zero; neither the premium index nor the interest component contributes to funding costs.
2. During Continuous Auctions: The funding rate is fixed at 0.005%, with funding collected every 4 hours.

This phased approach ensures stability during the pre-market trading period and prepares for the funding rate mechanism after the official launch. Understanding these rules helps traders better evaluate trading costs and develop optimized trading strategies.