In this lesson, you will learn how Automated Market Makers, or AMMs, make token trading possible without a centralized matching engine. You will see how prices are calculated, why slippage happens, how liquidity providers earn fees, and what risks real traders should watch before using an AMM.
What Is an Automated Market Maker?
An <strong>automated market maker</strong> is a trading protocol that lets users swap tokens through a <strong>smart contract</strong>, which is code that runs on a blockchain. Instead of matching a buyer with a seller, an AMM uses a pool of tokens called a <strong>liquidity pool</strong>.
In a traditional exchange order book, traders place bids and asks. A bid is the price someone wants to buy at, and an ask is the price someone wants to sell at. The trade happens when prices match.
In an AMM, there may be no direct counterparty. You trade against the pool itself. For example, an ETH/USDC pool holds ETH on one side and USDC on the other. If you want to buy ETH with USDC, you add USDC to the pool and remove ETH from it.
The people who deposit tokens into the pool are called <strong>liquidity providers</strong>, often shortened to LPs. They supply both assets and earn a share of trading fees. Traders get instant access to liquidity, while LPs get fee income for taking risk.
A simple AMM explained in one sentence is this: the pool uses a formula to adjust prices automatically as traders buy or sell.
How AMMs Set Prices
Most early AMMs use a formula called the <strong>constant product formula</strong>:
<strong>x × y = k</strong>
Here is what that means:
Imagine an ETH/USDC pool contains:
The pool price is roughly 3,000 USDC per ETH because 300,000 divided by 100 equals 3,000.
Now suppose a trader buys ETH by adding 30,000 USDC to the pool. The pool has more USDC and less ETH after the trade. Because ETH becomes scarcer inside the pool, the AMM raises the price of ETH for the next buyer.
This is the core of how AMMs work trading: each trade changes the balance of tokens in the pool, and the formula updates the price automatically.
This also creates a link between AMM prices and outside market prices. If ETH is 3,000 USDC in the pool but 3,050 USDC on another exchange, an <strong>arbitrage trader</strong> may buy ETH from the AMM and sell it elsewhere. Arbitrage means buying in one market and selling in another to capture a price difference. Their trading pushes the AMM price closer to the wider market price.
This process is important because AMMs do not know the true market price on their own. They rely on traders and arbitrage to keep pool prices aligned with other markets.
Slippage, Fees, and Pool Depth
When using an AMM, traders must understand <strong>slippage</strong>. Slippage is the difference between the expected trade price and the final executed price.
Slippage happens because your trade changes the pool balance. The larger your trade is compared with the pool, the more the price moves against you.
Example:
If you buy 5 ETH from Pool A, you remove half of the ETH in that pool. The price impact will be very large. If you buy 5 ETH from Pool B, you remove only 0.5 percent of the ETH, so the price impact is much smaller.
This is why <strong>pool depth</strong>, meaning the amount of liquidity in the pool, matters. Deeper pools usually offer better execution for larger trades.
AMMs also charge trading fees. A common fee might be 0.30 percent, though fees vary by protocol and pool. This fee is usually paid to liquidity providers, sometimes with a share going to the protocol itself.
Before placing a trade, a practical trader should check:
Many interfaces show these details before confirmation. Centralized exchanges, such as CoinW (https://www.coinw.com/en_US/register?r=3443555), may also list tokens that trade in DeFi, but AMM trading happens directly through blockchain smart contracts and wallets.
A useful rule is simple: if your trade is large relative to the pool, split the trade, look for a deeper pool, or compare routes through a DEX aggregator. A <strong>DEX aggregator</strong> is a tool that searches multiple decentralized exchanges to find better pricing.
Liquidity Providers and Impermanent Loss
Liquidity providers are essential to AMMs. They deposit assets into a pool so traders can swap. In return, they earn trading fees and sometimes extra token rewards.
However, LPs face a major risk called <strong>impermanent loss</strong>. Impermanent loss is the difference between holding tokens in your wallet and providing them to a pool when token prices change.
Example:
Your total position may still be worth more than before, but it may be worth less than if you had simply held 1 ETH and 3,000 USDC. That difference is impermanent loss. It becomes permanent if you withdraw liquidity at that point.
Fees can offset impermanent loss, especially in high-volume pools. But fees are not guaranteed to cover it. LPs should compare expected fees with price movement risk.
Intermediate traders should also know about <strong>concentrated liquidity</strong>. This allows LPs to provide liquidity only within a chosen price range, such as ETH between 2,800 and 3,400 USDC. It can improve capital efficiency, meaning the same money can support more trading volume. But it also increases management risk. If the market price leaves your range, your liquidity may stop earning fees until the price returns or you adjust the position.
Practical AMM Trading Checklist
AMMs are useful, but they should not be used blindly. A strong process helps reduce avoidable mistakes.
Before you trade, ask:
<strong>Slippage tolerance</strong> is the maximum price movement you accept before the transaction fails. If it is too low, the trade may fail and you still pay gas. If it is too high, you may receive a much worse price than expected, especially in fast markets or low-liquidity pools.
Be careful with very new tokens. Low liquidity can make prices easy to move. Some tokens also include transfer taxes or trading restrictions in their code. These can cause unexpected execution results.
For real traders, AMMs are best used with a clear plan. Check liquidity, compare prices, understand fees, and never assume the displayed pool price is the final execution price for your full order.