calculateTransactionFee

Introduction

The calculateTransactionFee method provides a way to determine the minimum network fee for a potential transaction without actually creating or broadcasting it. It serves as a "dry run" or simulation of the transaction creation process.

The endpoint uses the exact same internal logic and accepts the same parameters as addTransaction. It constructs the transaction in memory to accurately calculate its final byte size, determines the corresponding fee, and returns only the fee amount.

This is the recommended method for user interfaces that need to display the network fee to a user for confirmation before they commit to sending a transaction.

Request

Requests can be made using either HTTP POST with a JSON body or HTTP GET with URL query parameters.

Parameters

This method accepts the exact same parameters as the addTransaction method. You must provide enough information to construct a realistic transaction, such as the recipients and the source wallet.

Key Parameters:

• to: A hyphen-separated list of address_amount pairs. Required.
• from: (Optional) A list of specific inputs to use.
• wallet: The wallet address to source funds from (if from is omitted).

For a complete list and format details, please see the addTransaction documentation.

Example POST Request

POST /calculateTransactionFee
Content-Type: application/json

{
  "jsonrpc": "2.0",
  "method": "calculateTransactionFee",
  "params": {
    "wallet": "1EXSqPpj49ZmKiWF8stsMsMXVnSfkee7EzTaBakwNn9sJdaWm",
    "to": "16NBHjLGJnmWGWjoRj1Tz5TebgwhAtN2ewDThrDp1HfKuhJBo_12.5"
  },
  "id": 1
}

Example GET Request

GET /calculateTransactionFee?wallet=1EXSqPpj49ZmKiWF8stsMsMXVnSfkee7EzTaBakwNn9sJdaWm&to=16NBHjLGJnmWGWjoRj1Tz5TebgwhAtN2ewDThrDp1HfKuhJBo_12.5

Response

The response result is a single string representing the calculated fee.

Result Fields

Example Success Response

{
  "jsonrpc": "2.0",
  "result": "0.01000000",
  "id": 1,
  "error": null
}

Example Error Response

If the simulated transaction cannot be created (e.g., insufficient funds in the wallet), the endpoint will return an error.

{
    "jsonrpc": "2.0",
    "result": null,
    "id": 1,
    "error": {
        "code": -32001,
        "message": "Balance is too low"
    }
}

Behavioral Notes

• Simulation Only: This endpoint does not create, sign, or broadcast any transaction. It is a read-only calculation.
• Accuracy: Because it uses the full transaction creation logic (including automatic input selection if from is not specified), the returned fee is the accurate, size-dependent fee that the real transaction would require.
• Use Case: The primary purpose of this method is to provide a fee estimate for user confirmation. A typical application flow would be:
  1. User enters transaction details.
  2. Application calls calculateTransactionFee to get the network cost.
  3. Application displays the amount, recipient, and fee to the user and asks for confirmation.
  4. Upon confirmation, the application calls addTransaction with the same parameters to execute the transaction.