Bid Size vs Ask Size: What Every Trader Needs to Know
If you've ever looked at a trading platform and wondered what those numbers next to the bid and ask prices actually mean, you're not alone. Understanding bid size and ask size is one of those fundamentals that separates traders who read the market from traders who just react to it.
Let's cut straight to it.
Bid size is the total number of contracts (or shares) buyers are willing to purchase at the current bid price. Ask size is the total number of contracts sellers are offering at the current ask price. Together, they give you a real-time picture of supply and demand at the best available prices in the market.
That's the definition. But knowing what to do with this information is where the real edge starts.
The Basics: Bid Size and Ask Size Explained
Every market has two sides. There are buyers who want to get in at the lowest possible price, and sellers who want to exit at the highest possible price. The gap between those two prices is the spread, and the sizes attached to each side tell you how much liquidity exists right now.
Here's what each term means in plain terms:
Bid price: The highest price a buyer is currently willing to pay
Bid size: The number of contracts available at that bid price
Ask price: The lowest price a seller is currently willing to accept
Ask size: The number of contracts available at that ask price
If you see a market quoted as:
`Bid: 18,450.25 x 12 | Ask: 18,450.50 x 8`
That means 12 contracts are being bid at 18,450.25, and 8 contracts are being offered at 18,450.50. The spread is 0.25 points wide, and the market has moderate depth on both sides.
When you place a market order to buy, you're filling against the ask. When you sell, you're hitting the bid. The sizes tell you how many contracts you can transact before the price moves.
Bid Size vs Ask Size: What the Imbalance Tells You
Here's where bid and ask size goes from basic knowledge to actual trading insight.
When bid size is significantly larger than ask size, buyers are stacking up. More demand than supply at the best prices. That imbalance often precedes upward price movement because when those bids get exhausted, new bids tend to get placed higher.
When ask size dwarfs bid size, sellers are lined up. Supply is overwhelming demand at the current level. That kind of imbalance often precedes downward movement or at minimum, a struggle for price to push higher.
This is the foundation of reading order flow. You're not predicting the future, you're reading the present. What are the aggressive buyers and sellers actually doing right now?
"I learned more from Kyle in one hour than I have from hours and hours of Youtube, reading articles, and taking courses from other groups." - Mike
That reaction Mike had is pretty common when traders realize how much market structure they'd been ignoring. Bid and ask size is part of that structure. It's not a magic signal, but it's context that most retail traders completely tune out.
A Practical Example
Imagine you're watching NQ futures and the tape looks like this:
Bid: 18,422.00 x 45
Ask: 18,422.25 x 6
Forty-five contracts bid against six offered. That's a heavily skewed book. If you're looking for a long entry and you see that kind of imbalance at a key support level, it adds conviction. The market is telling you something. There's real buying interest sitting there.
Now flip it. Six bid, forty-five offered at a resistance zone you've been watching. That's a different story entirely. The sellers are stacked. A lot of supply needs to get absorbed before price moves higher.
Context matters enormously here. Bid/ask size imbalances in isolation are noise. Bid/ask size imbalances at a key price level, in the direction of the trend, with confluence from price action? That's signal.
How Bid Size and Ask Size Work in Options vs Futures
This is where a lot of traders get tripped up, because bid and ask size behaves differently depending on what you're trading.
Options Markets
Options are generally less liquid than futures. Even actively traded options contracts often have wider spreads and thinner sizes on both sides.
In options, bid size and ask size represent the number of option contracts available at those prices. One options contract typically represents 100 shares of the underlying. So a bid size of 10 means someone wants to buy 10 contracts, which controls 1,000 shares.
Key characteristics of bid/ask size in options:
Wider spreads are normal. A $0.10-$0.50 spread is common even in liquid options. In futures, that spread is usually 1-2 ticks.
Size is often smaller. You might see 5 or 10 contracts on each side versus hundreds in futures markets.
Market makers dominate. Options markets are primarily made by market makers who are constantly hedging. The sizes you see often reflect their willingness to take the other side, not organic retail flow.
Implied volatility affects spreads. When volatility spikes, market makers widen their spreads and reduce size to protect themselves from adverse selection.
When trading options, thin bid size means you may struggle to fill a large order at the quoted price. If you're trying to buy 20 contracts and bid size is only 5, you'll likely move the market against yourself.
Futures Markets
Futures, particularly index futures like NQ and ES, are among the most liquid markets in the world. This changes the bid/ask dynamic significantly.
Tighter spreads. NQ typically trades 0.25 points wide. ES is often at the minimum tick.
Much larger sizes. Hundreds or even thousands of contracts can sit on each side.
Electronic order book. Depth of market (DOM) is transparent and shows multiple price levels.
High-frequency influence. A significant portion of the size you see in futures is HFT activity. Sizes can vanish and reappear instantly.
For active futures traders, reading the DOM (Depth of Market) is a skill worth developing. You're not just looking at the top of the book, you're looking at the full stack of bids and offers across multiple price levels.
One thing I've noticed trading NQ for over a decade: large fake orders at key levels are common. A 200-contract offer sitting at resistance might evaporate the moment price approaches it. That's called spoofing, and while it's illegal, it still happens. Don't assume that a large bid or ask size will hold. Watch what actually trades, not just what's sitting there.
Quick Comparison: Options vs Futures
Typical spread: Options are wide ($0.10-$0.50+) | Futures are tight (1-2 ticks)
Typical size: Options have thin to moderate depth (5-50 contracts common) | Futures have deep (100-1,000+ contracts)
Market structure: Options dominated by market makers | Futures more diverse participants
Transparency: Options have limited depth visibility | Futures have full DOM available
HFT influence: Options are moderate | Futures are high
Liquidity risk: Options carry high slippage risk on large orders | Futures carry low slippage on standard sizes
Why Bid/Ask Size Matters for Your Execution
If you're entering and exiting small retail size, bid/ask spread is probably a bigger concern than the absolute size. But as your account and position sizes grow, understanding the depth matters more.
Here's the practical application:
Avoid thinly traded options at market. If you need to buy 20 contracts and the ask size is 3, you should either use a limit order or break up your order. Hitting the market when size is thin is a fast way to get terrible fills.
Use bid/ask size to confirm levels. If you're watching a support level on NQ and you see bid size building as price approaches it, that's institutions and algorithms defending that level. It's not a guarantee, but it's meaningful context for your read.
Watch for size changes. Sudden increases in bid size at a level often indicate institutional buying interest. Sudden increases in ask size at a level can indicate distribution. These shifts happen fast, so you need to be watching actively.
In our Trader's Thinktank community, we talk about this constantly during live sessions. Reading the tape and understanding order flow is one of the skills that separates developing traders from professionals, and it takes time and screen hours to develop properly.
The Spread: Bid and Ask Size in Context
Bid size and ask size don't exist in isolation. They're part of the full picture that includes:
The actual bid and ask prices
The spread between them
The size on each side
The price levels below and above (full DOM)
What's actually printing on the time and sales
A tight spread with small sizes can still move fast. A wide spread with large sizes suggests a more contested market. The spread itself is a transaction cost you pay every time you enter and exit a trade, which is why understanding it matters for profitability.
If you're trading options with a $0.50 spread on a $2.00 option, you're giving up 25% of the option's value in friction just to get in and out. That's an enormous hurdle, especially on shorter-term trades. This is one reason I gravitate toward futures for active day trading, and it's exactly the logic behind the Two Hour Trader approach, focused on liquid instruments during peak hours.
"Since being here I've had a much clearer understanding of when and where to trade. You've helped simplify my trading which has led to my first payout." - Martin Pena
How to Use Bid and Ask Size Practically
Here's a simple framework for incorporating bid/ask size into your trading:
Step 1: Know your instrument's normal range. What does typical bid and ask size look like on NQ during regular trading hours? Learn that baseline so you can recognize when something is abnormal.
Step 2: Check size before entering. Especially in options, always check that there's enough liquidity to fill your order without moving the market against you. In futures, check that the spread is tight and normal before entering.
Step 3: Watch for imbalances at key levels. When price approaches a support or resistance level you've identified through market structure analysis, look for bid/ask size imbalances that confirm or deny the level's significance.
Step 4: Use limit orders in thin markets. In options or futures with thin size, limit orders protect you from bad fills. Market orders in low-liquidity environments are a recipe for slippage.
Step 5: Don't overcomplicate it. Bid and ask size is one input among many. It doesn't override price action or trend. Use it to add context to decisions you're already making based on solid price action principles.
Common Mistakes Traders Make with Bid/Ask Size
A few things I see newer traders get wrong:
Treating bid size as a guaranteed fill. Size on the book can disappear before your order reaches it. This is especially true in futures where HFT algorithms are adding and removing orders constantly.
Ignoring spread on options. New options traders often focus on direction and forget that a wide spread is eating their edge before they even get started. Always calculate your effective entry cost including the spread.
Over-reading imbalances. Large bid size doesn't mean the market is definitely going up. It means there's demand at that price. If sellers step in aggressively, that bid size gets absorbed and price falls anyway. One data point, not a conclusion.
Not adjusting for time of day. Pre-market and after-hours bid and ask sizes are often much thinner. Spreads widen, sizes shrink. What looks like a normal entry during regular hours can be treacherous outside them.
For traders who want to remove execution uncertainty altogether, this is actually one of the core reasons the AutoPilot Trader exists. Consistent, unemotional execution at the right price levels, every time, without the second-guessing that comes from trying to read the tape in real-time.
"Unlike other gurus who may focus on trying to sell you indicators, Kyle has a singular focus on helping his members execute, with an emphasis on simplicity and discipline." - EH
The Bottom Line
Bid size and ask size are telling you something specific: how much the market wants to transact at the current best prices. That's real information.
In futures, where markets are deep and transparent, learning to read bid/ask size at key levels is a genuine skill worth building. In options, understanding that thin size and wide spreads are part of the cost structure helps you make better decisions about order type and position sizing.
Neither bid size nor ask size is a standalone trading signal. But combined with solid understanding of price action and market structure, they add real texture to your read of what's happening right now in the market.
Start with the basics. Know what you're looking at. Build from there.
