Buying/Selling Power

Power is one of the most critical and complex indicators in leveraged trading. It shows the maximum size order you can place for a specific instrument in a given direction at this moment. Essentially, it is your actual trading capability for that asset.

A crucial aspect is that Power can be greater than zero even if your Available Balance is zero. This happens when you place an order that reduces or completely closes an existing position. Such an order does not require additional margin but, instead, releases margin and the system allows its execution.

Formula

The formula for calculating trading power (opPower) consists of two parts:

$$\begin{aligned} \text{opPower}(\text{side}) = \ &\text{clVol}(\text{side}, \text{mPrice}) \\ + \ &\frac{\max\big[ 0, (\text{ab} - \text{clVol}(\text{side}, \text{mPrice}) \times \text{tFee}) \times \text{lev} + \text{clVol}(\text{side}, \text{p.avgPrice}) \big]}{1 + \text{lev} \times \text{tFee}} \end{aligned}$$

Structurally, the formula consists of two parts that reflect two different trading opportunities:

• Part 1: Power to close an existing position.

• Part 2: Power to open a new position based on available balance.

Detailed Breakdown of Parameters

Component	Description	Explanation
side	Order direction	Determines active components. For example, clVol equals zero if you are buying while already holding a long position.
clVol(...)	Part 1: Power for closing. This component calculates what portion of an existing position can be closed by an order in a given direction	Calculates the portion of an existing position that can be closed by placing an order in the chosen direction. If you hold a short position of 1 BTC and place a buy order, clVol equals the value of 1 BTC. If you have a long position of 1 BTC and place an additional buy order, clVol equals 0, as the action does not close the existing position.
max[0, (...)] / (...)	Part 2: Power for opening. This component calculates what additional position can be opened using the Available Balance	This part of the formula becomes active only if ab > 0. If ab = 0, this component will also be zero.
ab	Available Balance, calculated in the previous step	Forms the basis for calculating new buying power.
tFee	The commission for executing a taker order	The system pre-deducts potential fees from available funds to ensure you can pay them.
lev	The leverage set for this position	A multiplier converting available balance into trading power.
p.avgPrice	Average entry price of existing position	Used for more precise calculation of P&L and margin released when closing part of a position.
mPrice	Current mark price	Used to estimate current position and order values.

It is important to pay attention to the denominator (1 + lev * tFee). Note that the taker fee is charged on the full nominal volume of the trade (ab * lev), but it must be paid from the available balance (ab). This calculation prevents immediate margin shortages due to fee deductions upon order execution.

Practical Examples of Power Calculation

Example 1: Opening a new position with a positive ab

Condition: A trader has 1,000 USDT in their trading account and no open positions in BTC/USDT. They want to open a Long position with 10× leverage.

Calculation: clVol(...) = 0, as there is no existing position to close. Power will be calculated mainly from the second part of the formula. Approximately, it will be (1,000 × 10) / (1 + ...) which will be around 10,000 USDT (adjusted for the fee). The trader can open a position up to ~10,000 USDT.

Example 2: Closing an existing position with zero ab

Conditions: A trader has 0 USDT in their trading account. They have an open Long position of 1 BTC, which is currently worth 50,000 USDT. The trader wants to place a sell order to close this position.

Calculation: The second part of the formula (max[...] / (...)) will be 0, because ab = 0. The first part, clVol(...), will be equal to the nominal value of the existing LONG position, which is 50,000 USDT. Total Power to sell will be 50,000 USDT.

Conclusion: Despite having zero available balance, the trader has enough trading power to completely close their position.

FAQ

Why was my buy order rejected even though my position is in profit?

Unrealized profit does indeed increase your total account equity and pushes the liquidation price further away. However, the Available Balance, which is the basis for increasing an existing position or opening a new one, is calculated conservatively and only considers negative P&L (upnl_negative). Furthermore, even with a profit, if you are already using maximum leverage, you may not have the Power to add risk because all your capital is already engaged.

Why is my Available Balance zero, but I can still place a sell order?

This is a key concept explained in the Analysis of Trading Power. Your Power to close a position comes from the position itself, not from your free capital. The system always provides the ability to reduce risk, regardless of the available balance.

Should my Available Balance always equal my Buying Power?

No. As we explained above, these two values only match in one case: when you have no open positions. As soon as a position is opened, Power becomes a dynamic value that depends on the direction of your next order, while Available Balance remains a conservative measure of free funds.

I have an open position, but my buying and selling Power are both zero. Why?

This happens when the unrealized losses (upnl_negative) on your positions are so large that they have consumed not only your entire Available Balance but also almost the entire protective buffer between the initial and maintenance margin. Your account is on the verge of liquidation. In this state, the system blocks any trading actions (both increasing and decreasing the position) that could increase risk or require even minimal additional margin. The only way out of this situation is to either deposit more funds to increase collateral or wait for the market to turn in your favor.

How does the profit on my SOL position affect my ability to open a new position in BTC?

This question relates to the fundamental principle of cross margin. The unrealized "paper" profit on your SOL position does not increase your Available Balance. As we saw in the formula, only unrealized losses are considered for the AB calculation. Therefore, this profit does not directly give you "funds" to open a new position in BTC. However, this profit plays an important indirect role. If you have a losing position in another asset (e.g., ETH), the profit from SOL will compensate for it within the overall margin balance. This maintains the overall "health" of your account, prevents the initial margin (IM) from falling below the maintenance margin (MM) level, and thus preserves your ability to trade other assets for which you still have Power.

How do my open limit orders affect my Available Balance?

Open orders immediately impact Available Balance since the system employs a "worst-case scenario" approach:

• Increasing position orders immediately reserve Initial Margin, reducing Available Balance.

• Decreasing position orders (e.g., take-profit) indicate future margin release but do not increase AB immediately. The system incorporates this into the "worst-case scenario" calculation. AB only increases upon actual execution of these orders.