What is the Bid-Ask Spread?
The bid-ask spread is the difference between the highest price a buyer is willing to pay, known as the bid, and the lowest price a seller is willing to accept, known as the ask, for an asset. This spread represents an implicit transaction cost and serves as a key measure of market liquidity and efficiency.
Understanding Bid and Ask Prices
The bid price is the maximum amount buyers are currently willing to pay. If you want to sell immediately, you will receive the bid price. The ask price, also called the offer, is the minimum amount sellers are willing to accept. If you want to buy immediately, you will pay the ask price.
For example, if the ETH bid is $2,995 and the ask is $3,005, the spread is $10, or about 0.33%. To instantly buy and then sell, you would lose $10 per ETH to the spread alone, before any other fees.
Spread as a Liquidity Indicator
Tighter spreads indicate higher liquidity and more efficient markets. Major trading pairs like BTC/USDT on large exchanges typically have spreads under 0.1%. Less liquid pairs or smaller exchanges may have spreads of 1% or more, significantly increasing trading costs.
Spreads widen during low liquidity periods such as weekends and holidays, during high volatility events, and for less popular trading pairs. Unusually wide spreads signal increased trading costs and potentially greater price uncertainty.
Market Makers and Spreads
Market makers are entities that continuously provide liquidity by placing both buy and sell orders in the order book. They profit from the spread by buying at the bid and selling at the ask. Competition among market makers generally tightens spreads, benefiting traders with lower implicit costs.
In traditional finance, designated market makers are assigned to maintain orderly markets. In crypto, market making is competitive and permissionless, leading to varying spread quality across exchanges and pairs.
Spreads in DeFi
In AMM-based DeFi, the concept of spread manifests differently. There is no literal order book spread, but the effective spread appears as slippage and price impact. For trades against liquidity pools, the difference between buying and selling prices depends on pool depth and trade size.
Some DeFi protocols implement fee structures that function similarly to spreads, with swap fees acting as the cost difference between buying and selling.