Subscan recently made a change to show estimated fee and used fee, while if you query data from sidecar, partial fee + tip = estimated fee. What is this used fee and how is it calculated?

1 Answer 1


You can guess the fee before call the function querying the information from the payment RPC methods.

A little script to query your example is:

    const wsProvider = new WsProvider('wss://kusama-rpc.polkadot.io')
    const api = await ApiPromise.create({ provider: wsProvider });

    const blockHash = '0x9646cfeddaf4afd297f8a904f9458871b7203e6922cff502b3588af4c6cd1f0d';
    const { block } = await api.rpc.chain.getBlock(blockHash);

    // The extrinsic from your example(0x436d39517244cd5fc7c3d35dd08de0ccb62cb620868b5428db831857d4a952eb) is in block.extrinsics[7]
    const extrinsic = block.extrinsics[7].toHex();

    const queryFeeDetails = await api.rpc.payment.queryFeeDetails(extrinsic, blockHash);
    console.log('queryFeeDetails:', JSON.stringify(queryFeeDetails.toHuman(), null, 2));
    const queryInfo = await api.rpc.payment.queryInfo(extrinsic, blockHash);
    console.log('queryInfo:', JSON.stringify(queryInfo.toHuman(), null, 2));

This will give return you:

queryFeeDetails: {
  "inclusionFee": {
    "baseFee": "33.3333 µKSM",
    "lenFee": "489.9995 µKSM",
    "adjustedWeightFee": "5.4706 µKSM"
queryInfo: {
  "weight": "155,732,000",
  "class": "Normal",
  "partialFee": "528.8035 µKSM"

The estimated fee is partial fee, which is partial_fee = base_fee + len_fee + adjusted_weight_fee

But the adjusted_weight_fee might slightly change depends in which block the extrinsic is included. I am not 100% sure how subscan calculates it, but this is the Used Fee field.

Check this response to see an excellent explanation about how to calculate the final fee: https://substrate.stackexchange.com/a/4224/2762

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.