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Estimate Gas Fees (EIP-1559)

Fees are automatic. When you send a transaction with web3.Eth, Nethereum estimates EIP-1559 fees for you — you don't need to configure anything. This guide explains how the automatic estimation works and how to customize it when you need to.

dotnet add package Nethereum.Web3

The Default: You Probably Don't Need This Guide​

When you send any transaction through web3.Eth, fees are calculated automatically:

var web3 = new Web3(account, "https://mainnet.infura.io/v3/YOUR-PROJECT-ID");

// Fees are handled automatically — no configuration needed
var receipt = await web3.Eth.GetEtherTransferService()
    .TransferEtherAndWaitForReceiptAsync("0xRecipient", 1.11m);

Behind the scenes:

  • Default strategy: TimePreferenceFeeSuggestionStrategy (assigned since version 4.3.1)
  • Default transaction type: EIP-1559 (UseLegacyAsDefault = false)
  • Gas, nonce, fees: all calculated if not explicitly provided

If you're just sending transactions and they're going through fine, you're done. The rest of this guide is for when you need more control.

When You Need More Control​

You might want to customize fee estimation when:

  • High-priority transactions need faster inclusion (higher tip)
  • Gas-sensitive operations need cost optimization
  • Custom strategies fit your application's needs better

Strategy Comparison​

StrategyMethodBest For
TimePreferencePercentile-based from recent block pricesDefault — precise fee targeting with urgency levels
MedianMedian of fee history + base fee multiplierNext-block inclusion with congestion-aware pricing
SimplebaseFee × 2 + 2 GweiQuick estimate when accuracy is less important

Time Preference Fee Suggestion Strategy​

The default strategy. Based on Felfodi Zsolt's feehistory example, it analyzes recent block prices and suggests fees for different urgency levels — similar to the old "gas price oracle" in Geth but more reliable with EIP-1559's base fee signal.

Assign to the Transaction Manager​

The TimePreferenceFeeSuggestionStrategy is assigned by default, but you can set it explicitly:

var timePreferenceStrategy = web3.FeeSuggestion
    .GetTimePreferenceFeeSuggestionStrategy();
web3.TransactionManager.Fee1559SuggestionStrategy = timePreferenceStrategy;

Single Fee (Highest Priority)​

SuggestFeeAsync returns a single fee — the most urgent option:

var fee = await timePreferenceStrategy.SuggestFeeAsync();
Console.WriteLine("Max Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxFeePerGas.Value, Nethereum.Util.UnitConversion.EthUnit.Gwei)
    + " Gwei");
Console.WriteLine("Max Priority Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxPriorityFeePerGas.Value, Nethereum.Util.UnitConversion.EthUnit.Gwei)
    + " Gwei");

All Priority Levels​

SuggestFeesAsync returns all estimated fees, from highest to lowest priority:

var fees = await timePreferenceStrategy.SuggestFeesAsync();
var priority = 1;
foreach (var feeItem in fees)
{
    Console.WriteLine($"Priority level {priority}:");
    Console.WriteLine("  Max Fee Per Gas: " +
        Web3.Convert.FromWei(feeItem.MaxFeePerGas.Value,
            Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");
    Console.WriteLine("  Max Priority Fee Per Gas: " +
        Web3.Convert.FromWei(feeItem.MaxPriorityFeePerGas.Value,
            Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");
    priority++;
}

Very low MaxFeePerGas values or values matching MaxPriorityFeePerGas indicate that an estimate could not be made for that priority level.

Median Priority Fee History Suggestion Strategy​

Suggests a priority fee based on the median of fee history from previous blocks. The base fee is increased by a percentage depending on congestion. This ensures inclusion on the next block but may be more expensive.

Based on MyCrypto's implementation.

var medianStrategy = web3.FeeSuggestion
    .GetMedianPriorityFeeHistorySuggestionStrategy();
var fee = await medianStrategy.SuggestFeeAsync();
Console.WriteLine("Max Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxFeePerGas.Value,
        Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");
Console.WriteLine("Max Priority Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxPriorityFeePerGas.Value,
        Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");

Simple Fee Suggestion Strategy​

Gets the base fee, multiplies it by 2, and adds a default max priority fee of 2 Gwei:

var simpleStrategy = web3.FeeSuggestion
    .GetSimpleFeeSuggestionStrategy();
var fee = await simpleStrategy.SuggestFeeAsync();
Console.WriteLine("Max Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxFeePerGas.Value,
        Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");
Console.WriteLine("Max Priority Fee Per Gas: " +
    Web3.Convert.FromWei(fee.MaxPriorityFeePerGas.Value,
        Nethereum.Util.UnitConversion.EthUnit.Gwei) + " Gwei");

Apply Fees to a Contract Call​

You can set MaxFeePerGas and MaxPriorityFeePerGas on a contract FunctionMessage. Setting GasPrice instead converts the transaction to a legacy transaction:

using Nethereum.ABI.FunctionEncoding.Attributes;
using Nethereum.Contracts;
using System.Numerics;

[Function("transfer", "bool")]
public class TransferFunction : FunctionMessage
{
    [Parameter("address", "_to", 1)]
    public string To { get; set; }

    [Parameter("uint256", "_value", 2)]
    public BigInteger TokenAmount { get; set; }
}

var transferFunction = new TransferFunction();
transferFunction.MaxFeePerGas = fee.MaxFeePerGas;
transferFunction.MaxPriorityFeePerGas = fee.MaxPriorityFeePerGas;

Legacy Mode​

To use legacy GasPrice instead of EIP-1559:

web3.TransactionManager.UseLegacyAsDefault = true;

To learn more about EIP-1559, see the EIP-1559 FAQ.

Next Steps​