Перейти до основного вмісту

EVM Gas Fee Estimation: EIP-1559 baseFee, Priority Fees, and Why Fixed gasPrice Breaks

· 3 хв. читання
OverBlock Team
OverBlock Team
OverBlock Engineering

If you're setting gasPrice the same way across Ethereum, Polygon, and BSC, you're going to have problems. EIP-1559 fee mechanics are network-specific, and the right approach for Ethereum mainnet is wrong for Polygon and mostly irrelevant for BSC.

EIP-1559 mechanics (Ethereum mainnet)​

EIP-1559 replaced the single gasPrice field with two parameters:

baseFee - set by the protocol, changes every block. Burned (not paid to miners). Every node knows it.

maxPriorityFee (tip) - paid to the validator as an incentive. You set this based on how fast you want inclusion.

maxFeePerGas - your ceiling. Must be ≥ baseFee + maxPriorityFee. Excess over baseFee + tip is refunded.

The rule: if maxFeePerGas < baseFee, your transaction sits in the pool and doesn't get mined. This is the most common cause of stuck EIP-1559 transactions.

BaseFee adjustment formula​

BaseFee changes every block based on the previous block's fullness. The formula:

  • Block 100% full: nextBaseFee = currentBaseFee × 1.125
  • Block 50% full (target): nextBaseFee = currentBaseFee (unchanged)
  • Block 0% full: nextBaseFee = currentBaseFee × 0.875

Worst-case over N blocks (all blocks 100% full): worstCaseBaseFee = currentBaseFee × 1.125^N

This is the number you use for maxFeePerGas planning when you want to guarantee inclusion within N blocks regardless of congestion.

# Get baseFee prediction for next 5 blocks
curl "https://api.overblock.io/evm-fees/fee-advisor/next-base-fee?blocks=5" \
  -H "X-API-Key: your-token"
{
  "currentBaseFeeGwei": 45.2,
  "worstCaseIn5BlocksGwei": 81.3,
  "predictions": [
    { "block": "+1", "baseFeeGwei": 50.8 },
    { "block": "+2", "baseFeeGwei": 57.1 }
  ]
}

Polygon: high volatility, fast blocks​

Polygon uses EIP-1559 but with significantly more volatile baseFee. Spikes to 500-1000+ gwei during periods of high activity are common. Blocks arrive every ~2 seconds.

For Polygon, use more aggressive worst-case calculations. The evm-fees-advisor applies POLYGON_HIGH_VOLATILITY=true by default, which uses a larger multiplier in deadline calculations.

Don't use Ethereum mainnet fee estimates for Polygon transactions - the price ranges are completely different.

BSC: EIP-1559 in name only​

BSC implements EIP-1559 but the baseFee is effectively fixed at ~3 gwei. In practice, BSC fee estimation behaves more like legacy gasPrice - set gasPrice high enough above 3 gwei and your transaction will be included.

The evm-fees-advisor detects BSC (chain ID 56) and includes a note in the response: "BSC baseFee is stable (~3 gwei). Priority fee dominates."

eth_estimateGas: when to use it​

For ETH transfers: hardcode 21,000 gas. Every EVM node returns 21,000. Don't call eth_estimateGas.

For ERC-20 transfers: roughly 65,000 gas, but varies. Call eth_estimateGas.

For arbitrary contract calls: gas usage depends on contract state at execution time. Call eth_estimateGas close to submission time. Add a 20% buffer (gasLimit = estimatedGas × 1.2) to handle minor variance.

curl -X POST .../fee-advisor/estimate \
  -H "X-API-Key: your-token" \
  -d '{"from":"0x...","to":"0x...","data":"0xa9059cbb..."}'
{
  "estimatedGas": 65000,
  "recommendedGasLimit": 78000,
  "txType": "erc20_transfer",
  "wouldRevert": false
}

If wouldRevert: true, your transaction will fail. Fix the call parameters before submitting.

Recovering a stuck transaction​

EVM nodes require a minimum +10% on both maxFeePerGas and maxPriorityFee to accept a replacement transaction (unlike Bitcoin's BIP125 which only requires +1 sat/vB).

curl -X POST .../fee-advisor/stuck-tx \
  -d '{"currentMaxFeePerGasGwei": 40, "currentMaxPriorityFeeGwei": 1, "targetBlocks": 1}'

The response tells you whether to replace (with exact new values) or wait (if current fees are already competitive).

evm-fees-advisor covers all of this - EIP-1559 and legacy, all networks, per-transaction estimation - as a REST + SSE API.