Estimate Transaction Fees

Fireblocks provides clients with two API endpoints to estimate transaction fees:

1. Estimate Transaction Fee - Documentation
2. Estimate Network Fee - Documentation

Estimate Transaction Fee

The Estimate Transaction Fee endpoint is designed to simulate a real transaction and calculate its potential fee. This process considers factors such as the source and destination amounts, the number of inputs and outputs, and other relevant transaction details. Essentially, it mimics the actual transaction to determine what the fee would be if executed.

When using this endpoint, clients should be aware that it follows the same rules as creating a transaction. This includes requiring the relevant vault wallet in the vault account, ensuring the estimated transaction’s balance is in the wallet, and providing a valid destination.

While many clients implement logic to estimate the transaction fee before each execution, it is crucial not to call this endpoint for every minor transaction change. For example, in EVM-based transactions, the gas limit for transferring the base asset or a specific token usually remains the same (barring sudden surges in network fees). The main variable is the current network fee, which can be obtained using the second endpoint.

Estimate Network Fee

The Estimate Network Fee endpoint returns the current network fee for a specified network. This allows clients to calculate transaction fees or display the current network fee to their users. For instance, it provides the current gas price for ETH, which is part of the entire transaction fee formula, alongside the gas limit and other parameters.

The network fee response is cached for 30 seconds on the Fireblocks side. Clients should consider this interval when using this endpoint, as querying it more frequently than every 30 seconds does not provide additional value and the fee level value would remain the same.

Fee Levels

Both endpoints return estimated fees or network fees in three levels: LOW, MEDIUM, and HIGH. Here’s how these are determined for different transaction types:

EVM-Based Transactions

To simplify the gas calculation for each transaction, Fireblocks offers preset fees for both the Console (slow, medium, and fast) and the API (low, medium, and high). These fee calculations are based on recent blocks and a certain percentile of the data collected.

Fireblocks retrieves the latest block data every minute, inspecting the gas prices of recent blocks to determine the fee rate and automatically set the gas limit. In addition to verifying the latest data, Fireblocks also simulates the desired transactions to estimate the fee. The transaction parameters are sent to an API endpoint on the node, which returns an estimated transaction fee.

UTXO-Based Transactions

• High: Fees are based on the previous block’s fee.
• Medium: Fees are based on the average of the previous two blocks.
• Low: Fees are based on the average of the last four blocks.

Fireblocks’ API endpoints for estimating transaction fees provide clients with robust tools to ensure they can accurately predict and manage transaction costs. By using these endpoints, clients can maintain efficient and cost-effective operations while offering transparency and predictability in transaction fees to their users. Whether you are dealing with EVM-based, UTXO-based transactions or any other type of blockchain, understanding and utilizing these endpoints can significantly enhance your transaction management strategy.

Best Practices

Calling the Fee Estimation Endpoint

In some workflows, customers call the fee estimation endpoint for every transaction. However, this is not required for chains with relatively constant per-transaction fees, where fees depend mainly on network congestion and number of operations. In such cases, you can explicitly state the network fee instead (for example, on Stellar).

In these flows, the network fee can be cached for several seconds, accounting for differences between chains.

Fee Estimation Accuracy

Fee estimation endpoints return the estimated fee at the time of the call. The actual fee may change when the transaction is created due to factors such as network congestion or different UTXO selection caused by newer deposits.

Learn more about Fees

1. EVM Networks
2. UTXO Based Assets
3. Unique Calculations

Check out the Fee Management Developer Guide