What this gas tracker actually shows
Every transaction on an EVM blockchain costs gas, and the price of that gas changes block by block. This tracker pings six public RPC endpoints in parallel (Ethereum, Optimism, Arbitrum, Base, Polygon, BSC), pulls the base fee and the priority fee distribution from the last 5 blocks, then converts it into a USD cost estimate for the four most common transaction types.
You see the same numbers a wallet like MetaMask sees, except in one place, side by side. The page auto-refreshes every 30 seconds, which is roughly the rate at which Ethereum settles a new block, so the data stays honest without hammering the RPCs.
How to read each card
- Base fee is the part of the gas price set by the protocol itself, in gwei (1 gwei = 0.000000001 of the native token). It moves up when the previous block was more than half full, down when it was less. You always pay it, and after EIP-1559 it is burned, not paid to validators.
- Slow / Standard / Fast tiers are total gas prices (base plus priority). They come from the 25th, 50th, and 95th percentiles of the actual priority tips paid in the last 5 blocks. Standard is the realistic "should land in the next block or two" rate.
- Native transfer (21k gas) is the cheapest possible transaction: sending ETH, MATIC, or BNB from one address to another with no contract call.
- ERC-20 transfer (65k gas) is sending a token (USDC, USDT, your favorite memecoin) - about 3x more expensive than a native transfer because it writes to a contract storage slot.
- Uniswap swap (150k gas) is a representative DEX trade: token in, token out, one hop. Multi-hop or stableswap pools can be 2x to 3x this number.
- NFT mint (250k gas) is a typical mint: write to a new storage slot, emit a Transfer event, sometimes a small royalty payment. Complex collections with on-chain art can be much higher.
- Pause the auto-refresh with the switch in the header when you want to take a screenshot, compare numbers across chains without them moving, or just stare at a frozen gwei value while you decide whether to send.
When this is useful
Concrete scenarios where this tracker saves you money or time:
- Timing a big mainnet transaction. You are about to mint, swap, or bridge something expensive on Ethereum. You leave this tab open, wait for base fee to drop below your target gwei, then submit. A single afternoon of patience can cut a $40 transaction down to $8.
- Choosing the cheapest L2 right now. Optimism, Arbitrum, and Base all do the same thing, but their fees vary. You glance at three cards and pick whichever one is currently quietest - often a 5x to 10x difference between them on a busy day.
- Setting a max fee for a long-running script. You are about to run a bot or batch script that will submit dozens of transactions over the next hour. You see the 95th percentile number and set that as your max gas, knowing 95% of recent blocks went through cheaper.
- Diagnosing a stuck transaction. Your transaction is pending. You check what standard gas is right now - if your original tx was below this number, it will not land. You speed it up (replace by fee) with a higher priority and unstick it.
- Picking the right chain for a user-facing app. You are building something that hands out NFTs. NFT mint on Ethereum mainnet costs $5 to $50, on Polygon it costs cents. You see the spread, you pick Polygon, your users do not abandon checkout.
- Sanity-checking a wallet's gas estimate. MetaMask suggests 80 gwei. Is that fair? You check this tracker - if the standard tier is 25, MetaMask is 3x overpriced (often the case after a fee spike). You manually edit it down and save real money.
Related tools: Ethereum unit converter (gwei to ether math), crypto address validator, function selector.
Questions and answers
Gas is the fuel unit of an EVM blockchain - every operation a smart contract does (add two numbers, store a value, emit an event) has a fixed gas cost, and you pay the total in the native token of that chain. Different transactions burn different amounts of gas: a plain transfer is 21,000 units, a Uniswap swap is around 150,000, a complex DeFi deposit can be 500,000 or more. Gas price (in gwei) is what you pay per unit of gas.