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You decide how much computation to allow and how much to pay. The two key controls are the gas limit and the fee parameters.

This lesson covers both, including the EIP-1559 fee model.

The gas limit is the maximum amount of gas you authorize a transaction to consume.

A simple ETH transfer needs 21000; complex contract calls need more. Setting it too low causes an out-of-gas revert.

If execution uses more gas than your limit, it stops and reverts all state changes.

Critically, you still pay for the gas already burned — running out of gas does not give you a refund.

Each block also has a block gas limit — the total gas all its transactions may consume.

This caps how much computation fits in one block, keeping block processing fast across the network.

Originally, fees worked as a blind auction: you bid a gas price and validators picked the highest bids.

This led to overpaying and unpredictable fees during congestion. EIP-1559 reformed this in 2021.

EIP-1559 introduced a base fee — a per-block fee set automatically by the protocol based on network demand.

The base fee rises when blocks are full and falls when they are empty, making fees more predictable.

The base fee is burned — permanently destroyed rather than paid to validators.

This removes the incentive for validators to artificially inflate fees and makes ETH mildly deflationary under heavy use.

To incentivize validators, you add a priority fee, or tip, on top of the base fee.

A higher tip encourages validators to include your transaction sooner during congestion.

You set a maxFeePerGas — the most you will pay per gas unit total. You also set a maxPriorityFeePerGas for the tip.

If the base fee is below your max, you are refunded the difference. You never overpay beyond your cap.

Wallets and tools call eth_estimateGas to predict how much gas a transaction needs.

Good estimates avoid out-of-gas failures while not over-reserving gas unnecessarily.

The gas limit caps computation; EIP-1559 splits the price into a burned base fee plus a validator tip.

Your maxFeePerGas guards against overpaying while ensuring inclusion.

You learned that:

• The gas limit caps how much gas a transaction may use
• Running out of gas reverts but still costs you
• EIP-1559 uses a burned base fee plus a validator tip
• maxFeePerGas caps your total cost per unit

Next: nonces and ordering.