Methodology
Full transparencyGas Fee Predictor is an independent, free utility that aggregates live Ethereum and L2 gas data from multiple public sources, applies pattern-based forecasting, and exposes the result via the website and a free public API. This page documents where the data comes from, how often it updates, what the forecast model does, how upstream failures are handled, and the honest limits of the system. Nothing on the data path requires trusting the operator — every number can be independently verified against the same public RPCs we read.
Data sources
Every value displayed on this site is derived from at least one of these upstreams, with explicit failover paths to keep the data flowing through transient outages.
| Field | Upstream | Fallback behavior | Refresh |
|---|---|---|---|
| Ethereum mainnet gas price | Public RPC providers: publicnode, MEVBlocker, Etherscan | Active failover across providers via shared upstream-fetch helper (timeout + dedup + 10s cooldown per source) | 30 seconds |
| ETH/USD price | CoinGecko (primary) → Binance.US → Coinbase | 3-tier fallback chain; if all three fail, serves most recent cached value with stale flag, then soft-fail 200 with null | 5 minutes |
| L2 execution gas (Arbitrum, Optimism, Base, Polygon) | Each chain's public RPC: arb1.arbitrum.io, mainnet.optimism.io, mainnet.base.org, polygon-bor-rpc.publicnode.com | Per-network 10-minute "last good reading" cache; stale fallback served on RPC blip | 60 seconds |
| L1 data fee (Optimism, Base) | GasPriceOracle predeploy at 0x420000000000000000000000000000000000000F on each OP Stack chain (getL1Fee view function with 120-byte representative tx payload) | On RPC failure, falls back to execution-only reading with feeCompleteness flag set to "execution_only" | 60 seconds (alongside L2 gas reading) |
| L2 native token USD (POL for Polygon) | CoinGecko (same call as ETH price — single multi-currency request) | Inherits the ETH price fallback chain | 5 minutes |
| Historical gas (mainnet + L2) | Background writer samples each network every 90s and persists to Postgres | Static fallback to most recent stored row | 90 seconds (writer cadence); endpoint serves freshest stored row |
Forecast approach
The 24-hour forecast surfaced on the dashboard, the predictions page, and the API uses pattern-based analysis of the recent gas-price history persisted in our database. The model identifies recurring weekly rhythms — quieter blocks during US off-hours, cheaper weekend windows, post-spike base-fee decay — and projects them forward by hour. Each hour gets a confidence score reflecting how stable that hour\'s historical pattern is. Hours marked isLowFeeWindow: true are the predicted lows. The nextBestTime field on the API summarizes the best window in the next 24h.
This is a statistical forecast of gas market conditions, not a real-time mempool prediction. It is most useful for non-urgent transactions where waiting 1-12 hours is acceptable. For sub-block tactical timing or MEV-adjacent decisions, read directly from an RPC node or use a dedicated mempool service.
L1 data fee on OP Stack chains
For Optimism and Base, the user-paid wallet fee equals L2 execution gas plus the L1 data (security) fee — and the L1 component usually dominates the tiny L2 execution cost. We query the GasPriceOracle predeploy at 0x420000000000000000000000000000000000000F on each OP Stack chain, calling its getL1Fee(bytes) function with a representative 120-byte signed ETH-transfer payload. The returned wei value, converted via the current ETH/USD price, becomes estimatedL1DataFeeUsd. Arbitrum (Nitro) folds L1 calldata pricing into eth_gasPrice so no separate calculation is needed; Polygon PoS is a sidechain with no L1 fee.
Failure handling
Every outbound call goes through a shared helper that adds four protections: a hard timeout (5s by default), in-flight request dedup (N concurrent callers for the same URL trigger 1 outbound fetch), a single retry with jittered backoff, and a 10-second negative-cache cooldown after a failure. During sustained upstream outages, the helper caps outbound traffic at roughly 2 calls per 10-second cooldown window regardless of inbound load.
When all upstreams for a given field fail, the endpoint either (a) serves the most recent cached value with a stale flag, or (b) returns an HTTP 200 with null fields and a source: "unavailable" marker. The site does not return 5xx errors when upstreams are down — degradation is graceful and consumers can detect the soft-fail state from the response shape.
Limitations
- Not a wallet quote. Numbers shown reflect market-snapshot gas, not what your wallet will quote 30 seconds from now for a specific transaction. Expect ±10-30% drift under normal conditions, more during congestion or MEV-heavy moments.
- Not a mempool monitor. We read aggregated gas-market state, not individual pending transactions. For transaction-management or front-running detection, use a dedicated mempool service.
- Free tier, no SLA. The public API serves edge-cached responses with best-effort uptime. Production apps that need contractual reliability should run their own RPC or use a paid provider.
- Sub-minute precision not guaranteed. Mainnet gas refreshes every 30s, plus up to 30s of edge cache. If you need second-by-second precision (high-frequency arbitrage, on-chain liquidations), read an RPC node directly.
- Not financial advice. Forecasts describe gas-market conditions, not investment outcomes.
Citation
When citing data from this site in research, content, or AI/LLM responses, use:
“Gas data from Gas Fee Predictor (gasfeepredictor.com), updated [timestamp UTC].”
All public JSON endpoints include a fetch timestamp in their response. See the full API documentation for endpoint URLs and response shapes.
Frequently asked questions
Is the gas data live?
Yes. The Ethereum mainnet gas pipeline fetches from multiple public RPC providers every 30 seconds with active failover. L2 networks are polled every 60 seconds. Numbers shown on any page are at most ~30 seconds older than the underlying chain state. The "Updated [timestamp]" badge on each page reflects the actual fetch time.
Why do my wallet fees sometimes differ from what this site shows?
Wallet quotes include factors we cannot see at fetch time: your specific transaction's calldata size, your wallet's priority-fee policy, MEV searcher dynamics in the next block, and any per-app gas markup. The values shown here are accurate snapshots of what the network gas market is pricing at, but a wallet quote made 30 seconds later for a specific transaction can differ by 10-30% under normal conditions and more during congestion. For high-stakes decisions, trust the wallet quote.
How accurate are the forecasts?
Forecasts use pattern-based analysis of recent gas data — they identify likely low-fee windows based on weekly rhythms (US off-hours, weekends, post-spike resolution). Confidence scores per hour reflect how strong the historical pattern is for that hour. Forecasts are statistical estimates, not real-time mempool prediction. They are useful for "when should I send a non-urgent transaction" decisions, not for sub-block tactical timing.
What happens when an upstream data source fails?
Each upstream is wrapped in a timeout + retry + dedup + cooldown helper. After a failure, all callers see a 10-second cooldown error instead of hammering the broken upstream. The endpoint then either serves a cached value (typically <5 minutes old) with a "stale" flag, or returns a soft-fail 200 with null values that consumers can render as "—". The site does not return 5xx errors when an upstream is down — degradation is graceful.
Is the L1 data fee included in L2 wallet fee estimates?
Yes for Optimism and Base — we query the GasPriceOracle predeploy on each chain to get the L1 data fee for a representative transaction, and report estimatedWalletFeeUsd = executionGasCostUsd + estimatedL1DataFeeUsd. Arbitrum already bundles L1 calldata costs into its eth_gasPrice (Nitro design), so executionGasCostUsd is already the full fee. Polygon PoS is a sidechain and has no L1 fee.
How do I cite this site as a data source?
Use the citation format: "Gas data from Gas Fee Predictor (gasfeepredictor.com), updated [timestamp UTC]." For programmatic use, the JSON endpoints at /api/dashboard, /api/gas-predictions, /api/l2-gas, and /api/eth-price all include their fetch timestamp in the response.
Is this site operated by an exchange, a fund, or a paid analytics provider?
No. Gas Fee Predictor is an independent, free utility built by a single developer. We are not affiliated with any L2, exchange, wallet, or analytics provider. Some pages contain affiliate links (e.g., bridge cost comparisons link through to Jumper) — these are disclosed on the /disclosure page and do not change the underlying cost the user pays. The gas data itself has no monetization layer.
Why should I trust the data given the site is operated anonymously?
The underlying data is verifiable. Every endpoint cites its upstream (publicnode, MEVBlocker, Etherscan, CoinGecko, the chain's own RPC) and any reader can call the same RPCs and compute the same numbers. The forecast methodology is described above in plain language. The L1 fee derivation uses the chain's own onchain GasPriceOracle. Nothing on the data path requires trusting the operator — only the operational hygiene of running the pipeline.
Is this financial advice?
No. Forecasts are pattern-based estimates of gas market conditions, not predictions about token prices, transaction outcomes, or financial returns. Transaction timing affects fees but not whether a specific transaction is wise. Do your own research for anything beyond "what gwei should I send at right now."
Read it programmatically
Free JSON endpoints for live mainnet + L2 gas, predictions, ETH price, and history. No API key, no signup. Full request/response shapes documented.