payment_queryInfo - JSON-RPC Method

Returns the fee information for the given signed extrinsic.

Parameters

Parameter	Type	Required	Description
extrinsic	string	Yes	SCALE-encoded signed extrinsic in hex

cURL Example

curl -X POST https://api-moonbase-alpha.n.dwellir.com/YOUR_API_KEY \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc":"2.0",
    "id":1,
    "method":"payment_queryInfo",
    "params":["0x<signed_extrinsic_hex>"]
  }'

Tip: First compute a fully signed extrinsic (matching the nonce from system_accountNextIndex). Then pass the same hex here to get the final fee.

JavaScript (polkadot.js)

import { ApiPromise, WsProvider } from '@polkadot/api';

async function estimate(exHex: string) {
  const api = await ApiPromise.create({ provider: new WsProvider('wss://api-moonbase-alpha.n.dwellir.com/YOUR_API_KEY') });
  const info = await api.rpc.payment.queryInfo(exHex);
  console.log('PartialFee:', info.partialFee.toString());
  await api.disconnect();
}

Returns

ExtrinsicFeeDetails including weight and partialFee.

Notes

• Provide the exact signed payload you intend to broadcast; otherwise the result may differ.
• Combine with payment_queryFeeDetails for a breakdown of fee components.