> For the complete documentation index, see [llms.txt](https://docs.getblock.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.getblock.io/api-reference/filecoin-fil/native-api/filecoin_gasestimatemessagegas.md).

# Filecoin.GasEstimateMessageGas - Filecoin

Example code for the Filecoin.GasEstimateMessageGas JSON RPC method. Complete guide on how to use Filecoin.GasEstimateMessageGas JSON RPC in GetBlock Web3 documentation.

This method fills in the unset gas fields of a message, estimating the gas limit, fee cap, and premium needed for timely inclusion. The message is returned with its gas fields populated.

## Parameters

| Parameter | Type   | Required | Description                                                    |
| --------- | ------ | -------- | -------------------------------------------------------------- |
| message   | object | Yes      | The message to estimate gas for                                |
| sendSpec  | object | No       | Optional send specification, such as a max fee; null to omit   |
| tipsetKey | array  | Yes      | Tipset key to estimate against; empty array for the chain head |

## Request

{% tabs %}
{% tab title="cURL" %}
{% code overflow="wrap" %}

```bash
curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{"jsonrpc": "2.0", "method": "Filecoin.GasEstimateMessageGas", "params": [{"To": "f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", "From": "f3ukhj6tpkgxjknu54opiaej2vrjz7nh7gzodkqlhpfphc6gxkogzmojv2cnlpgcuwkvnyhloctnc6lmlvceuq", "Value": "1000000000000000000", "Method": 0}, null, []], "id": "getblock.io"}'
```

{% endcode %}
{% endtab %}

{% tab title="JavaScript" %}
{% code title="example.js" %}

```javascript
const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        jsonrpc: '2.0',
        method: 'Filecoin.GasEstimateMessageGas',
        params: [{"To": "f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", "From": "f3ukhj6tpkgxjknu54opiaej2vrjz7nh7gzodkqlhpfphc6gxkogzmojv2cnlpgcuwkvnyhloctnc6lmlvceuq", "Value": "1000000000000000000", "Method": 0}, null, []],
        id: 'getblock.io'
    })
});

const data = await response.json();
console.log(data.result);
```

{% endcode %}
{% endtab %}

{% tab title="Python" %}
{% code title="example.py" %}

```python
import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'Filecoin.GasEstimateMessageGas',
        'params': [{"To": "f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", "From": "f3ukhj6tpkgxjknu54opiaej2vrjz7nh7gzodkqlhpfphc6gxkogzmojv2cnlpgcuwkvnyhloctnc6lmlvceuq", "Value": "1000000000000000000", "Method": 0}, null, []],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Response

```json
{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "To": "f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq",
        "From": "f3ukhj6tpkgxjknu54opiaej2vrjz7nh7gzodkqlhpfphc6gxkogzmojv2cnlpgcuwkvnyhloctnc6lmlvceuq",
        "Value": "1000000000000000000",
        "GasLimit": 2200000,
        "GasFeeCap": "101520",
        "GasPremium": "100178",
        "Method": 0,
        "Nonce": 43
    }
}
```

## Response Parameters

| Field      | Type    | Description                                     |
| ---------- | ------- | ----------------------------------------------- |
| GasLimit   | integer | Estimated maximum gas units for the message     |
| GasFeeCap  | string  | Estimated maximum fee per gas unit, in attoFIL  |
| GasPremium | string  | Estimated priority fee per gas unit, in attoFIL |
| Nonce      | integer | Nonce assigned to the message                   |

## Use Cases

* **Fee Estimation**: Populate gas fields before signing a message
* **Cost Preview**: Show the estimated cost of a message
* **Inclusion Tuning**: Set gas for timely block inclusion
* **Wallet Flows**: Prepare a fully specified message for signing

## Error Handling

| Error Code | Message         | Description                                                 |
| ---------- | --------------- | ----------------------------------------------------------- |
| -32602     | Invalid params  | A parameter is missing or has the wrong type or format      |
| 1          | Actor not found | The address or actor does not exist in the requested tipset |
| -32603     | Internal error  | The node failed to process the request                      |