eth_estimateGas

Gas on BNB Smart Chain is paid in BNB, and eth_estimateGas tells you how much a transaction will consume before you commit. The node dry-runs the call against current state on its geth-equivalent EVM, then returns the gas units the operation would burn. A BEP-20 transfer, a PancakeSwap swap, a fresh contract deployment: all of them estimate the same way. Aim it at https://bsc.therpc.io/YOUR_API_KEY (chain ID 56). The simulation never reaches a validator and changes nothing on-chain. Only the estimate comes back.

Use cases

Derive the gas limit to stamp on a transaction before signing it with BNB.
Estimate the up-front cost of deploying a new BEP-20 token or DeFi contract to BSC.
Probe whether a swap or transfer would succeed, since a reverting path returns an error instead of a number.
Power live fee figures in BSC wallets and dApp confirmation screens.

Parameters

#	Name	Type	Required	Description
1	`transaction`	object	Yes	Transaction object. `to` is required for calls; omit `to` for contract deployments. Optional: `from`, `gas`, `gasPrice`/`maxFeePerGas`/`maxPriorityFeePerGas`, `value`, `data`.
2	`blockTag`	string	No	Block state to simulate against. Defaults to `latest`.Default: `latest`

Response

Type	Description
string	Hex-encoded gas estimate. The node typically adds a small safety buffer above the raw simulation result.

Example request

1curl https://bsc.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_estimateGas",
7    "params": [
8        {
9          "to": "0x8894E0a0c962CB723c1976a4421c95949bE2D4E3",
10          "data": "0x"
11        },
12        "latest"
13      ],
14    "id": 1
15  }'

Try it live in the BNB Smart Chain playground.

Errors & troubleshooting

Code	Message	Cause
`3`	`execution reverted`	The simulated transaction reverted; the estimate cannot be produced.
`-32000`	`gas required exceeds allowance`	Estimated gas exceeded the block gas limit or the supplied gas cap.
`-32602`	`invalid argument`	Malformed transaction object.

Common pitfalls

The figure is a best-effort guess, not a ceiling. Pad it by roughly 20% so a branch that costs slightly more does not strand the transaction out of gas.
A simulated revert yields a JSON-RPC error (often code 3), not a gas number. Branch on that case instead of parsing a missing result.
On BSC's ~3s blocks, contract state can move between estimate and inclusion, so a Venus or PancakeSwap call may end up consuming a different amount than predicted.

Supported networks

Mainnet — Chain ID: 56
Testnet — Chain ID: 97