# 1.2 Cross-chain Quota and Fees

#### 1.2.1. Querying Cross-chain Quota

The available quota for each token must be queried separately. The API endpoint is as follows:

```json
<https://bridge-api.wanchain.org/api/quota?fromChainType=[fromChainType]&toChainType=[toChainType]&symbol=[symbol]>
```

Use the values returned by the `tokenPairs` API for `fromChainType`, `toChainType`, and `symbol` in the request parameters.

**Example:**

[`https://bridge-api.wanchain.org/api/quota?fromChainType=WAN&toChainType=ARETH&symbol=USDC`](https://bridge-api.wanchain.org/api/quota?fromChainType=WAN\&toChainType=ARETH\&symbol=USDC)

**Response Example:**

```json
{
  "success": true,
  "data": {
    "symbol": "USDC",
    "minQuota": "0",
    "maxQuota": "5000000000"
  }
}
```

**Usage Notes**

* Choose the appropriate `chainType` based on the desired cross-chain direction.
* For instance, when transferring from Arbitrum to BSC, set `fromChainType=ARETH` and `toChainType=BNB`. Conversely, when transferring from BSC to Arbitrum, use `fromChainType=BNB` and `toChainType=ARETH`.
* The `maxQuota` value in the response is expressed using the decimals of `fromToken`.

#### 1.2.2 Querying Cross-chain Fees

The fee API returns two types of fees:

* **networkFee**: Charged in the native token of the blockchain (e.g., ETH on Ethereum, BNB on BSC).
* **operationFee**: Charged in the token being transferred (e.g., USDT is charged when it is being transferred).

**Fee Calculation Rules**

* If `isPercent` is `false`, the fee is charged as a fixed amount based on the `value` field.
* If `isPercent` is `true`, the `value` represents a percentage and must be multiplied by the transfer amount.
* When fees are percentage-based, `minFeeLimit` and `maxFeeLimit` define the minimum and maximum fee thresholds.

**API Endpoint:**

```json
<https://bridge-api.wanchain.org/api/fee?fromChainType=[fromChainType]&toChainType=[toChainType]&tokenPairID=[tokenPairID]>
```

Use the values from `tokenPairs` for `fromChainType`, `toChainType`, and `tokenPairID`.

**Example 1: Querying Fees for USDT Transfer from Arbitrum to Ethereum**

```json
<https://bridge-api.wanchain.org/api/fee?fromChainType=ARETH&toChainType=ETH&tokenPairID=191>
```

**Response Example:**

```json
{
  "success": true,
  "data": {
    "networkFee": {
      "value": "7000000000000000",
      "isPercent": false
    },
    "operationFee": {
      "value": "0",
      "isPercent": true
    }
  }
}
```

This means a network fee of `7000000000000000` wei (0.007 ETH) is charged on Arbitrum.

**Example 2: Querying Fees for BTC Transfer from Ethereum to Bitcoin**

```json
<https://bridge-api.wanchain.org/api/fee?fromChainType=ETH&toChainType=BTC&tokenPairID=14>
```

**Response Example:**

```json
{
  "success": true,
  "data": {
    "networkFee": {
      "value": "0",
      "isPercent": false
    },
    "operationFee": {
      "value": "0.006",
      "isPercent": true,
      "minFeeLimit": "35000",
      "maxFeeLimit": "50000000"
    }
  }
}
```

This means no network fee is charged, and BTC is charged at 0.6% of the transfer amount, with a minimum fee of 35000 satoshis (0.00035 BTC) and a maximum fee of 50000000 satoshis (0.5 BTC).

#### 1.2.3 Aggregated Query for Cross-chain Quota and Fees (quotaAndFee API)

**API Endpoint:**

[`https://bridge-api.wanchain.org/api/quotaAndFee?fromChainType=[fromChainType]&toChainType=[toChainType]&tokenPairID=[tokenPairID]&symbol=[symbol]`](https://bridge-api.wanchain.org/api/quotaAndFee?fromChainType=%5BfromChainType%5D\&toChainType=%5BtoChainType%5D\&tokenPairID=%5BtokenPairID%5D\&symbol=%5Bsymbol%5D)

**Example:**

```jsx
<https://bridge-api.wanchain.org/api/quotaAndFee?fromChainType=ETH&toChainType=BTC&tokenPairID=14&symbol=BTC>
```

**Response Example:**

```jsx
{
  "success": true,
  "data": {
    "symbol": "BTC",
    "minQuota": "0",
    "maxQuota": "5061694752",
    "networkFee": {
      "value": "0",
      "isPercent": false
    },
    "operationFee": {
      "value": "0.006",
      "isPercent": true,
      "minFeeLimit": "35000",
      "maxFeeLimit": "50000000"
    }
  }
}
```