Gas is the fuel of EVM blockchains. Every transaction pays for the computation and storage it consumes.
What Is Gas?
Gas measures computational work. Simple transfers cost a fixed amount (21,000 gas); complex contract interactions cost more because they execute more operations and touch more storage.
Two numbers determine what you pay:
- Gas limit — the maximum gas you allow the transaction to consume. Unused gas is refunded.
- Gas price — what you pay per unit of gas, usually denominated in gwei (a small fraction of the native coin).
Fee = gas used × gas priceGas Used vs. Gas Limit
If a transaction runs out of gas mid-execution, it fails and reverts — but the fee for the work already performed is still charged. That’s why wallets estimate the gas limit with headroom.
OpenScan.AI shows both values on every transaction page, plus the effective fee in the native coin.
Base Fee and Priority Fee
Many EVM chains burn a protocol-set base fee per block and let senders add a priority fee (tip) to incentivize validators. When the network is congested, base fees rise; when it’s quiet, transactions are cheap.
Reading Gas Data in the Explorer
- Transaction page — gas limit, gas used, gas price, and the total fee.
- Block page — aggregate gas used versus the block gas limit, a measure of network congestion.
- Address page — total fees spent by an account over time.
Why Gas Matters
- Cost planning — check current gas prices before broadcasting large batches of transactions.
- Debugging — “out of gas” is the most common cause of failed contract calls; the explorer shows exactly where execution stopped.
- Token operations — every ERC-20 transfer and NFT mint consumes gas on top of any protocol fee.
Next Steps
- Transactions — where gas is spent.
- Blocks — how block gas limits shape throughput.