/transaction/fee-estimate - Polkadot

Example code for the /transaction/fee-estimate REST method. Complete guide on how to use /transaction/fee-estimate REST in GetBlock Web3 documentation.

This endpoint estimates the fee and weight for a submitted transaction without broadcasting it.

On GetBlock's unified endpoint, Asset Hub is the default network. To call this endpoint against the Relaychain, add an /rc prefix to the path (for example, /rc/transaction/fee-estimate).

Endpoint

POST /transaction/fee-estimate

Body Parameters

Field	Type	Required	Description
tx	string	Yes	A SCALE-encoded transaction, hex-encoded

Request

cURL

curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/transaction/fee-estimate' \
--header 'Content-Type: application/json' \
--data-raw '{"tx": "0x4d028400d43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d01..."}'

JavaScript

example.js

const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/transaction/fee-estimate', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
  "tx": "0x4d028400d43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d01..."
})
});
const data = await response.json();
console.log(data);

Python

example.py

import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/transaction/fee-estimate',
    json={
  "tx": "0x4d028400d43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d01..."
}
)
print(response.json())

Response

{
  "weight": {
    "refTime": "133700000",
    "proofSize": "3593"
  },
  "class": "Normal",
  "partialFee": "15960000000"
}

Response Fields

Field	Type	Description
weight	object	Dispatch weight (refTime and proofSize)
class	string	Dispatch class
partialFee	string	Estimated fee in Planck, excluding tip

Use Cases

• Fee Preview: Show the estimated fee before signing

• Budgeting: Estimate fees for batches of transactions

• Wallet UX: Display expected costs to users

• Automation: Gate submissions on fee thresholds