How Tick Size Affects Your Limit Orders
Tick size directly determines whether your limit order can get to the front of the queue, and how much extra cost you pay when it's filled.
It defines the smallest possible difference between two prices on the order book, and your limit order price must be a multiple of this increment. This seemingly basic parameter impacts your limit orders through three key channels: the bid-ask spread, queue priority, and the phenomenon of passive market making.
1. First, Figure Out the Tick Size of the Market You're Trading
Tick sizes vary across markets and even across different price ranges within the same market. You must verify it before placing an order.
On decentralized derivatives platforms (e.g., Synthetix): Each market has an independently set tick size. You can place any limit order at a price that respects the tick size multiple, but orders are matched on a price-time priority basis—higher bids and lower asks get filled first.
On centralized exchanges (e.g., Binance Futures): Each trading pair has a clearly defined minimum price fluctuation. For example, the BTCUSDT perpetual contract uses 0.10 USDT, while ETHUSDT uses 0.01 USDT. If you enter a price that isn't a multiple of the tick size, the system will automatically round it down (e.g., entering 0.22 with a 0.1 tick size gets adjusted to 0.2).
In traditional financial markets (Hong Kong stocks, US stocks, futures): Tiered quotation rules also apply. The higher the price, the larger the minimum price variation, and regulators may adjust these periodically.
Completion standard: Before placing an order, find the Trading Rules or contract specifications page on your trading interface to confirm the exact "minimum price movement" or tick size for that particular pair.
2. Assess How Tick Size Affects Your Trading Costs
Tick size directly dictates how much price concession you need to make to get filled.
Case A: Large tick size. Spread costs are higher. If you want to "jump the queue" and get filled immediately, you need to give up at least one tick of price space. In markets where the bid-ask spread equals exactly one tick, a marketable buy order will be executed against the best ask at a price one full tick higher, directly increasing your entry cost. Research suggests that under old rules, relative bid-ask spreads for funds could be as high as around 1%.
Case B: Small tick size. The bid-ask spread is typically compressed narrower, improving liquidity. Both HKEX and the U.S. SEC have reduced minimum quoting units to narrow spreads and lower transaction costs for investors. However, an overly small tick size also means others can jump ahead of your order with a very small price improvement, and your liquidity-providing limit order may easily get pushed to the back of the queue.
3. Judge the "Survivability" of Your Order in the Queue
The larger the tick size, the fewer price levels on the order book. Your order may be "safer," but it may also become more "passive."
Large tick size encourages a "locked" market: When the tick size is too large relative to the stock price, many traders will place large orders on both the best bid and the best ask to capture the tick spread, effectively acting as market makers. This can make it hard for prices to break through, leaving your limit orders unfilled for a long time.
Small tick size leads to more intense order competition: Since moving one tick costs very little, high-frequency traders or market makers can use a minimal price advantage to step in front of you. Strategies here rely more on speed and algorithms rather than pure price advantage.
4. Risk Warning: Important Price Limit Mechanism ("Price Cage")
In markets like China's A-share market, tick size also interacts with the "price cage" mechanism. A buy order price cannot exceed 102% of the benchmark price or exceed the benchmark price by 10 minimum price increments (whichever is lower). This means that if the tick size is small (e.g., for low-priced stocks), your order price band is severely compressed. Practices like placing a high-priced buy order to fill quickly or a low-priced sell order can easily become invalid.
How to confirm you've correctly placed your limit order:
Before placing your order, verify two things: first, what the specific tick size is for that trading pair; second, whether your price is truly a multiple of that tick size (otherwise the system will modify it). If you place a buy order slightly above the current best bid but it doesn't get filled for a long time, check the tick size—if the spread is already smaller than one tick, the order book price may be stuck. You'll need to improve your price by at least one tick to move to the front of the queue.
