Funding rate
For Pro mode (orderbook perpetual contracts)
What is the funding rate?
In perpetual futures contracts, the funding rate is a periodic payment exchanged between traders holding long and short positions. This mechanism helps ensure that the contract price stays close to the underlying spot market price.
Positive funding rate: When the contract price is above the mark price, long traders pay short traders.
Negative funding rate: When the contract price is below the mark price, short traders pay long traders.
This payment encourages traders to take positions that push the contract price back in line with the spot price.
Funding rate formula
Funding rate = Premium index + Interest rate
Premium index reflects the difference between the perpetual contract price and the spot price.
Interest rate is fixed at 0.03% per day on AsterEX.
For example, if the premium index is 0.015%, the total funding rate would be 0.045%.
Premium index calculation
Premium index = [max(0, Impact bid price − Index price) − max(0, Index price − Impact ask price)] ÷ Index price
Where:
Index price = Weighted average price from external spot exchanges
Impact bid price = Average price to sell a fixed notional value using the current bid depth
Impact ask price = Average price to buy a fixed notional value using the current ask depth
How to calculate impact bid price
To determine the Impact bid price, identify the level in the order book where the cumulative quote value exceeds the Impact Margin Notional (IMN).
To help visualize the calculation, the following table shows how quote notional values accumulate across levels in the order book:
In this table:
Quote Notional Quantity = price × quantity × contract multiplier
Accumulated Quote Notional Quantity is the sum of quote notional values up to that level.
Once the accumulated quote notional exceeds the IMN, the corresponding level is used in the final Impact Bid (or Ask) Price formula.
If:
Contract multiplier × ∑px × qx > IMN
and
Contract multiplier × ∑px-1 × qx-1 < IMN
Then level x is used to calculate the Impact Bid Price using: Impact Bid Price = IMN / [(IMN − Contract Multiplier × ∑px−1 × qx−1) / px + Contract Multiplier × ∑qx−1]
Where:
px = Price at level x
qx = Quantity at level x
IMN = Impact margin notional (predefined value)
Contract multiplier = Multiplier for the contract (usually 1)
Example order book (bid side)
Assume the bid-side of the order book is:
1
100
5
2
99
10
3
98
15
To calculate the Impact Bid Price, accumulate quoted value by level until it meets or exceeds the IMN (Impact Margin Notional). Then apply the formula above using the correct level data.
Funding amount
The funding amount is how much you will actually pay or receive based on the funding rate.
Funding amount = Position size × Mark price × Funding rate
This value is transferred between long and short traders depending on the direction of the funding rate. Aster does not charge or receive funding — it is a peer-to-peer transfer.
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