fee-estimation

EIP-1559 Fee Estimation with Nethereum

NuGet: Nethereum.RPC

Source: Fee1559SuggestionDocExampleTests

Required Usings

using System.Numerics;
using Nethereum.Hex.HexTypes;
using Nethereum.RPC.Eth.DTOs;
using Nethereum.RPC.Fee1559Suggestions;

Fee Components

EIP-1559 splits gas fees into baseFee (protocol-set, burned) and priorityFee (tip to validator). Users set maxPriorityFeePerGas (tip ceiling) and maxFeePerGas (total ceiling). Actual cost = min(baseFee + priorityFee, maxFeePerGas).

Fee1559 Model

Holds all fee components in a single object.

var fee = new Fee1559
{
    BaseFee = 20_000_000_000,
    MaxPriorityFeePerGas = 2_000_000_000,
    MaxFeePerGas = 42_000_000_000
};

Strategy 1: Simple (Default)

Fixed priority fee of 2 Gwei. MaxFee = 2 * baseFee + priorityFee. Fast, no RPC calls beyond latest block.

var defaultPriority = SimpleFeeSuggestionStrategy.DEFAULT_MAX_PRIORITY_FEE_PER_GAS;
// 2,000,000,000 (2 Gwei)

// Usage with Web3:
// var strategy = new SimpleFeeSuggestionStrategy(web3.Client);
// Fee1559 fee = await strategy.SuggestFeeAsync();

Strategy 2: Median Priority Fee History

Uses eth_feeHistory to compute median priority fee from recent blocks. Applies a baseFee multiplier that decreases as baseFee rises.

Base Fee Multiplier Tiers

var strategy = new MedianPriorityFeeHistorySuggestionStrategy();

strategy.GetBaseFeeMultiplier(30_000_000_000);   // 2.0x  (< 40 Gwei)
strategy.GetBaseFeeMultiplier(50_000_000_000);   // 1.6x  (40-100 Gwei)
strategy.GetBaseFeeMultiplier(150_000_000_000);  // 1.4x  (100-200 Gwei)
strategy.GetBaseFeeMultiplier(300_000_000_000);  // 1.2x  (>= 200 Gwei)

Estimate Priority Fee from Fee History

var feeHistory = new FeeHistoryResult
{
    OldestBlock = new HexBigInteger(100),
    BaseFeePerGas = new[]
    {
        new HexBigInteger(20_000_000_000),
        new HexBigInteger(21_000_000_000)
    },
    GasUsedRatio = new decimal[] { 0.5m },
    Reward = new[]
    {
        new[] { new HexBigInteger(1_000_000_000) },
        new[] { new HexBigInteger(1_500_000_000) },
        new[] { new HexBigInteger(2_000_000_000) },
        new[] { new HexBigInteger(2_500_000_000) },
        new[] { new HexBigInteger(3_000_000_000) }
    }
};

var estimate = strategy.EstimatePriorityFee(feeHistory);

Suggest Max Fee Using Multiplier

var maxPriorityFee = new BigInteger(2_000_000_000);
var baseFee = new HexBigInteger(30_000_000_000);

Fee1559 result = strategy.SuggestMaxFeeUsingMultiplier(maxPriorityFee, baseFee);
// result.MaxFeePerGas > baseFee (includes multiplier headroom)
// result.MaxPriorityFeePerGas == maxPriorityFee

Strategy 3: Time Preference

Returns an array of Fee1559 suggestions factoring in urgency. Uses 100 blocks of fee history. Best for UIs offering slow/medium/fast options.

var strategy = new TimePreferenceFeeSuggestionStrategy();

// Build fee history (normally from eth_feeHistory RPC)
var feeHistory = new FeeHistoryResult
{
    OldestBlock = new HexBigInteger(1000),
    BaseFeePerGas = baseFees,   // HexBigInteger[101]
    GasUsedRatio = gasUsedRatio // decimal[100]
};

var tip = new BigInteger(2_000_000_000);
Fee1559[] fees = strategy.SuggestFees(feeHistory, tip);

foreach (var fee in fees)
{
    // fee.MaxFeePerGas >= fee.MaxPriorityFeePerGas
}

Default Behavior in Web3

Web3's TransactionManagerBase defaults:

• Strategy: TimePreferenceFeeSuggestionStrategy (NOT Simple)
• Transaction type: EIP-1559 (UseLegacyAsDefault = false)
• Auto-calculate: CalculateOrSetDefaultGasPriceFeesIfNotSet = true

Override the strategy:

web3.TransactionManager.Fee1559SuggestionStrategy =
    new SimpleFeeSuggestionStrategy(web3.Client);

Force legacy transactions:

web3.TransactionManager.UseLegacyAsDefault = true;
// Or provide GasPrice in TransactionInput — legacy is used automatically

Strategy Comparison

Using with Web3 (Live)

// Simple
var simple = new SimpleFeeSuggestionStrategy(web3.Client);
Fee1559 fee = await simple.SuggestFeeAsync();

// Median
var median = new MedianPriorityFeeHistorySuggestionStrategy(web3.Client);
Fee1559 fee = await median.SuggestFeeAsync();

// TimePreference
var timePref = new TimePreferenceFeeSuggestionStrategy(web3.Client);
Fee1559[] fees = await timePref.SuggestFeesAsync();