# Estimate fee

## Overview

This function calculates the fees required for the query. If the Gateway contract's `query()` sends less than the required fee, it is reverted as `InvalidFee`.

```solidity
struct QueryRequest {
  uint32 dstChainId;
  address to;
  uint256 height;
  bytes32 slot;
}

function estimateFee(
  address lightClient,
  QueryType.QueryRequest[] memory queries
) public view returns (uint256);
```

<table><thead><tr><th width="174.5">Field</th><th>Description</th></tr></thead><tbody><tr><td><code>lightClient</code></td><td>The address of the contract is to be verified</td></tr><tr><td><code>queries</code></td><td>An array of <code>QueryRequest</code> data</td></tr></tbody></table>

## How to calculate

In `estimateFee()`, the function calculates the sum of the fees for each actor, such as Relayer, Oracle, etc.

There are two main categories of the fee;

* Protocol fee
* Verification fee

Of these, only the Protocol fee is calculated by Gateway contract's `estimateFee()` itself. The verification fee is calculated by [`estimateQueryFee()`](/docs/protocol/light-client/estimate-fee.md) of the Light Client Contract.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://futaba.gitbook.io/docs/protocol/gateway/estimate-fee.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.