What Is Bid-Ask Imbalance?
Bid-ask imbalance measures the relative size of buy orders (bids) versus sell orders (asks) on the order book. If there are $10M in bids and $5M in asks near the current price, there's a 2:1 bid imbalance — significantly more buying interest than selling interest. This imbalance suggests short-term upward price pressure.
How Bid-Ask Imbalance Works
Order book imbalance is calculated as: (Bid Volume - Ask Volume) / (Bid Volume + Ask Volume). Values range from -1 (all asks, no bids) to +1 (all bids, no asks). The calculation is typically done within a certain depth range (e.g., within 1% of the mid-price) to focus on the most relevant orders.
Why It Matters for Traders
Bid-ask imbalance is a leading short-term indicator: price tends to move toward the side with less depth (path of least resistance). A strong bid imbalance often precedes upward moves; a strong ask imbalance precedes downward moves. However, be aware of spoofing — large orders placed to create an apparent imbalance that are pulled before being hit.
How Perps Traders Use This
For CEX perpetual futures, treat bid-ask imbalance as context around entries, exits, and risk, not as a standalone signal. Pair it with funding, open interest, and liquidation heat so one indicator does not drive the whole book.
Formula and Worked Example
Example numbers only (not a live quote).
If your account equity is $10,000 and you risk 0.5% per idea, the cash risk budget is $50. With a stop 1% away from entry on a linear USDT-margined perp, notional size is about $5,000 before leverage optics. Size from stop distance first, then pick leverage that fits the margin mode.
Common Mistakes
- Treating a single print of bid-ask imbalance as a trade signal without checking funding, open interest, and your liquidation price.
- Mixing venue conventions (coin-margined vs USDT-margined, cross vs isolated) and reading the wrong mark.
- Copying example numbers from a glossary into live size without checking the current book depth and fee schedule.
- Ignoring related terms that change the meaning of the print on a given day.
