getFeeForMessage

getFeeForMessage asks a Solana node what a specific transaction message will cost to land, pricing it against a recent blockhash and returning the answer in lamports (1 SOL = 1,000,000,000 lamports). You pass the base64-encoded message — the part of the transaction that the fee is calculated from — and the node replies with the exact lamport charge for that message, or null if the blockhash it was built on has already expired. Call it through the TheRPC Solana endpoint at https://solana.therpc.io/YOUR_API_KEY.

Use cases

• Show a wallet user the precise lamport fee for the message they are about to sign, instead of a guessed estimate.
• Budget the total lamport cost of a batch of SPL token or SOL transfers by pricing each message before you assemble the batch.
• Replace the deprecated getFees flow: build the message, price it per-message here, and pair it with getRecentPrioritizationFees for any priority surcharge.

Parameters

Response

Example request

1curl https://solana.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5  "jsonrpc": "2.0",
6  "id": 1,
7  "method": "getFeeForMessage",
8  "params": [
9    "AQABAg...",
10    {}
11  ]
12}'

Errors & troubleshooting

Common pitfalls

• Pass the transaction message, base64-encoded — not the full signed transaction. Sending the whole signed payload here is a common cause of an Invalid params (-32602) response.
• A null value in the wrapped result means the blockhash the message references has expired. Fetch a fresh one with getLatestBlockhash, rebuild the message, and price it again.

Supported networks

• Mainnet
• Devnet

See also

• getLatestBlockhash
• getRecentPrioritizationFees
• isBlockhashValid