Track 1 · Mechanics · lesson 7

Base fee and tip

8 min

Gas measures how much work. This lesson is about what that work costs, which is a separate question with a much stranger answer.

Your fee is:

gas used × (base fee + priority fee)

The base fee is a thermostat, not an auction.

The base fee is a thermostat

Blocks target being half full. After a block that ran over half, the base fee rises. After one that ran under, it falls. The adjustment is capped at 12.5% per block, so it moves fast but not instantly.

Crucially, the base fee is burned — destroyed, not paid to anyone.

Burning looks wasteful until you ask the alternative. If validators received the base fee, they would have every reason to stuff blocks with their own fake transactions to drive it up, then collect it back.

Burning removes that incentive completely. The fee has to go somewhere nobody benefits from, and nowhere is the only such place.

The priority fee is the actual bid

On top of the base fee you add a tip, which does go to the validator. That is the part you compete on when you want to go first.

Most of the time the tip is small. When something is being minted, or a large liquidation is available, tips spike to absurd levels for a few blocks.

Predict

The base fee is burned rather than paid to validators. What does that do to ETH's supply during busy periods?

Nothing — the ETH is transferred, not destroyedSupply can shrink, if more is burned than issued to validatorsSupply always shrinks, because burning always exceeds issuance

Why your transaction is stuck

Three failure modes, and the fix differs for each:

Base fee rose above your max. Your transaction is not competitive at all until demand falls. Replace it with a higher cap.
Your tip is too low. You are competitive but always last in line.
A lower nonce is stuck. Nothing later from your account can move until the earlier one clears, whatever you pay.

That third one catches people repeatedly. Your transactions form a queue you cannot reorder.

Check

You set max fee 100 gwei. The base fee at inclusion is 30 and you tipped 2. What do you pay per gas?

100 gwei — the maximum you authorised32 gwei — base fee plus tip30 gwei — the base fee only

Worth remembering

Fee = gas used × (base fee + priority fee).
The base fee is an automatic thermostat targeting half-full blocks, moving at most 12.5% per block.
The base fee is burned so validators cannot profit by inflating it — which can shrink ETH supply when busy.
The tip is the real bid for position and goes to the validator.
Max fee is a ceiling, not a price. Setting it high costs nothing.