Get the Token Balance of an address - RPC Call (ERC-20 or compatible)

Tatum provides you access to the blockchain via RPC.

Here's a guide on how to retrieve the token balance of an ERC-20 token from a blockchain address via RPC call. This makes use of standard eth_call via balanceOf() to call a SmartContract ABI.

Steps

Step_1: Fetch the Smart Contract Address

• For example USDC over ETH: 0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48

Step_2: Fetch the Wallet Address

From which you want to retrieve the token balance

• For example: 0xCD531Ae9EFCCE479654c4926dec5F6209531Ca7b

Step_3: Make an RPC call with the method eth_call

Example request:

• "to" is the ContractAddress for USDC
• "data" has three parts:
  • Method ID: 70a08231 - This is the 4-byte function selector for ABI balanceOf(address).
  • Padding: "000000000000000000000000"
  • Wallet Address: CD531Ae9EFCCE479654c4926dec5F6209531Ca7b - The address to query the balance for, padded to 32 bytes (64 characters) CD531Ae9EFCCE479654c4926dec5F6209531Ca7b
  • The full data field will be: "0x70a08231" + "000000000000000000000000" + "CD531Ae9EFCCE479654c4926dec5F6209531Ca7b"

curl --location 'https://api.tatum.io/v3/blockchain/node/ethereum-mainnet/' \
--header 'Content-Type: application/json' \
--header 'x-api-key: ••••••' \
--data '{
    "jsonrpc":"2.0",
    "method":"eth_call",
    "params":[
      {
        "to": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
        "data": "0x70a08231000000000000000000000000CD531Ae9EFCCE479654c4926dec5F6209531Ca7b"
      },
      "latest"
    ],
    "id":1
  }'
//response:
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x0000000000000000000000000000000000000000000000000000000000f4240"
}

Step_4: Interpret and convert the response.

Example request:

1. The "result" field is the balance in hexadecimal (Wei).
2. Convert the result in hex to decimal and adjust for the token's decimals (USDC uses 6 decimals).

# Example response balance in hexadecimal
balance_hex = "0x0000000000000000000000000000000000000000000000000000000000f4240"

# Convert hexadecimal to integer
balance_wei = int(balance_hex, 16)

# USDC uses 6 decimals
decimals = 6

# Convert to human-readable format
balance_human_readable = balance_wei / (10 ** decimals)

print(balance_human_readable)

Good to know

• Depending on the Smart Contract code, the method to fetch the balance may vary.
• Tatum staff generally does not troubleshoot RPC requests, unless there's an error explicitly related to our infrastructure.