# Tick Sizes and Lot Sizes

> Tick sizes set the minimum price step and lot sizes set the minimum trade size. Learn how both are chosen, how they shape spreads and queues and recent rule changes.

Source: https://learn.tradelabsai.com/market-structure/tick-sizes-and-lot-sizes/  
Track: Market Structure · Level: Intermediate · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Tick Sizes and Lot Sizes", https://learn.tradelabsai.com/market-structure/tick-sizes-and-lot-sizes/

Every market has two basic design choices that quietly shape how trading works: the **tick size**, the smallest allowed price change, and the **lot size**, the standard or minimum trading quantity. They look like technical details, but they influence spreads, liquidity, queue lengths, trading costs and even which traders thrive in a market.

## Tick size: the price grid

The tick size defines the grid of allowed prices. A one cent tick means a stock can trade at $50.00 or $50.01 but not in between. See [Ticks and Tick Size](https://learn.tradelabsai.com/markets/ticks-and-tick-size/) for examples across markets.

### Why tick size matters

| If the tick is large relative to price | If the tick is small relative to price |
|---|---|
| Spreads are forced to at least one wide tick | Spreads can be very narrow |
| Long queues form at each price | Short queues spread across many prices |
| Queue position becomes valuable | Price improvement by tiny amounts is easy |
| Market makers earn more per trade | Competition squeezes market maker profits |

A one cent tick is 0.1% of a $10 stock but only 0.002% of a $500 stock. For very liquid, low priced stocks, the one cent minimum can be wider than the spread would naturally be, creating long queues. For high priced stocks, prices can move in tiny steps relative to their value.

### Tick size rules and changes

- **US stocks:** Regulation NMS has long set a minimum of one cent for stocks priced $1 or more. In 2024, the SEC adopted amendments allowing a half cent tick for stocks with consistently very tight spreads.
- **The Tick Size Pilot (2016 to 2018)** tested wider five cent ticks for some small US stocks to see if they would improve liquidity; results were mixed, with wider spreads and higher costs for many investors.
- **Decimalisation:** US stocks were quoted in fractions such as 1/16 of a dollar until 2001, when markets switched to decimals, which narrowed spreads dramatically.
- **Europe** uses tick size tables that vary with price and liquidity under MiFID II.
- **Futures exchanges** set ticks per contract, such as 0.25 index points for the E-mini S&P 500.

## Lot size: the quantity grid

The lot size is the standard unit of trading.

| Market | Lot conventions |
|---|---|
| US stocks | 100 shares is a round lot; fewer is an odd lot; fractional shares exist at many brokers |
| Forex | Standard 100,000 units, mini 10,000, micro 1,000. See [Lots: Standard, Mini and Micro](https://learn.tradelabsai.com/forex/lots-standard-mini-and-micro/) |
| Futures | One contract is the minimum; micro contracts offer smaller exposure |
| Options | One contract, usually 100 shares |
| Crypto | Minimum order sizes set by each exchange, often tiny fractions of a coin |

### Why lot size matters

- **Accessibility:** large minimum sizes keep small traders out; micro lots and fractional shares let them in.
- **Quote display:** in US stocks, odd lot orders were historically not reflected in the official best bid and offer. Recent SEC rules redefined round lots for higher priced stocks so that the displayed quote better reflects available prices.
- **Position sizing:** large lots make precise risk control harder for small accounts.

**Example: Lot size and risk control**
A forex trader with $2,000 wants to risk $20 on a trade with a 40 pip stop on EUR/USD. The right size is $0.50 per pip, five micro lots. If the broker only offered standard lots ($10 per pip), the smallest trade would risk $400, 20% of the account. Small lots make sensible sizing possible.

## How design choices affect you

1. **Expect long queues** in liquid low priced stocks; price improvement or marketable orders may be needed to get filled. See [Fill Probability and Queue Position](https://learn.tradelabsai.com/orders/queue-position/).
2. **Spread costs** are higher as a percentage on low priced stocks with a one cent tick.
3. **Use micro contracts and lots** to size positions properly.
4. **Know the tick value** of every futures contract you trade. See [Tick Size and Tick Value](https://learn.tradelabsai.com/futures/tick-size-and-tick-value/).

## Frequently asked questions

### What is a round lot?

The standard trading unit, traditionally 100 shares for US stocks. Orders for fewer shares are odd lots.

### Why do tick sizes matter?

They set the minimum spread and shape how orders queue, affecting costs and how easily you get filled.

### Can I trade fractions of a share?

Many brokers offer fractional shares by pooling orders internally, though exchanges themselves trade whole shares.

## Sources

- Wikipedia, [Tick size](https://en.wikipedia.org/wiki/Tick_size)
- Wikipedia, [Round lot](https://en.wikipedia.org/wiki/Round_lot)

## Continue learning

- Next lesson: [Opening and Closing Auctions](https://learn.tradelabsai.com/market-structure/opening-and-closing-auctions/)
- Previous lesson: [Price Discovery](https://learn.tradelabsai.com/market-structure/price-discovery/)
- Related: [Price Discovery](https://learn.tradelabsai.com/market-structure/price-discovery/): Price discovery is how markets combine buyers' and sellers' information into a price. Learn how it works, where it happens and what helps or harms it.
- Related: [Ticks and Tick Size](https://learn.tradelabsai.com/markets/ticks-and-tick-size/): A tick is the smallest price move an asset can make. Learn tick sizes in stocks, futures, forex and crypto, how tick value works and why it matters for costs.
- Related: [Tick Size and Tick Value](https://learn.tradelabsai.com/futures/tick-size-and-tick-value/): Tick size is a future's smallest price move; tick value is what it is worth per contract. Learn to calculate P&L, risk per trade and position size from ticks.
- Related: [Lots: Standard, Mini and Micro](https://learn.tradelabsai.com/forex/lots-standard-mini-and-micro/): Forex positions are measured in lots. Learn standard, mini, micro and nano lot sizes, their pip values, the exposure they create and how to choose the right size.
- Related: [Fill Probability and Queue Position](https://learn.tradelabsai.com/orders/queue-position/): Your place in the order queue decides whether a limit order fills. Learn how queues work, how to estimate fill probability and why fills can be a warning sign.
- Related: [Bid-Ask Spread](https://learn.tradelabsai.com/markets/bid-ask-spread/): The bid-ask spread is the gap between the best price to buy and the best price to sell. Learn how to read it, what it costs you and how to pay less of it.