GET /v2/amplify/calculateWithdrawalFee returns the fee a user would be charged for redeeming a specific offerAmount of shares for a given wantAsset. The backend resolves the account’s configured FeeModule via the indexer and calls calculateOfferFees() on-chain.
Use this endpoint to preview fees in a withdrawal confirmation UI before submitting the order via GET /v2/amplify/withdraw.
The withdrawal endpoint itself already accounts for fees internally — you do not need to call calculateWithdrawalFee before preparing withdrawal calldata. It exists purely for display.
Parameters
| Parameter | Type | Required | Description |
|---|
offerAmount | string | Yes | Share amount to withdraw in base units (decimal string, 18 decimals) |
wantAsset | string | Yes | ERC-20 token address the user wants to receive |
vaultAddress | string | Yes | BoringVault contract address (0x + 40 hex chars) |
chainId | number | Yes | EVM chain ID |
Example
curl
Node.js
Python
Go
Java
curl "https://api.paxoslabs.com/v2/amplify/calculateWithdrawalFee?\
offerAmount=1000000000000000000&\
wantAsset=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48&\
vaultAddress=0xbbbb000000000000000000000000000000000001&\
chainId=1" \
-H "x-api-key: pxl_your_key"
const url = new URL(
"https://api.paxoslabs.com/v2/amplify/calculateWithdrawalFee"
);
url.searchParams.set("offerAmount", "1000000000000000000");
url.searchParams.set("wantAsset", "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48");
url.searchParams.set("vaultAddress", "0xbbbb000000000000000000000000000000000001");
url.searchParams.set("chainId", "1");
const resp = await fetch(url, {
headers: { "x-api-key": process.env.AMPLIFY_API_KEY! },
});
const data = await resp.json();
console.log(
`Fee: ${data.feeAmount} (${data.offerFeePercentage.percentage}%), flat: ${data.flatFee}`
);
import requests
resp = requests.get(
"https://api.paxoslabs.com/v2/amplify/calculateWithdrawalFee",
headers={"x-api-key": "pxl_your_key"},
params={
"offerAmount": "1000000000000000000",
"wantAsset": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
"vaultAddress": "0xbbbb000000000000000000000000000000000001",
"chainId": 1,
},
)
data = resp.json()
print(
f"Fee: {data['feeAmount']} "
f"({data['offerFeePercentage']['percentage']}%), "
f"flat: {data['flatFee']}"
)
params := url.Values{
"offerAmount": {"1000000000000000000"},
"wantAsset": {"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"},
"vaultAddress": {"0xbbbb000000000000000000000000000000000001"},
"chainId": {"1"},
}
req, _ := http.NewRequest("GET",
"https://api.paxoslabs.com/v2/amplify/calculateWithdrawalFee?"+params.Encode(),
nil)
req.Header.Set("x-api-key", os.Getenv("AMPLIFY_API_KEY"))
resp, _ := http.DefaultClient.Do(req)
defer resp.Body.Close()
String feeUrl = String.format(
"https://api.paxoslabs.com/v2/amplify/calculateWithdrawalFee?" +
"offerAmount=%s&wantAsset=%s&vaultAddress=%s&chainId=%d",
"1000000000000000000",
"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
"0xbbbb000000000000000000000000000000000001",
1);
HttpRequest req = HttpRequest.newBuilder()
.uri(URI.create(feeUrl))
.header("x-api-key", System.getenv("AMPLIFY_API_KEY"))
.GET().build();
HttpResponse<String> resp = httpClient.send(req, HttpResponse.BodyHandlers.ofString());
JsonObject data = JsonParser.parseString(resp.body()).getAsJsonObject();
Response
{
"feeAmount": "0.05",
"offerFeePercentage": { "bps": 25, "percentage": "0.2500" },
"flatFee": "1.05"
}
| Field | Type | Description |
|---|
feeAmount | string (decimal) | Total fee for this offerAmount + wantAsset, human-readable (scaled by the want-asset decimals) |
offerFeePercentage.bps | number | Fee percentage in basis points (25 = 0.25%) |
offerFeePercentage.percentage | string | Human-readable percentage with 4 decimals (e.g. "0.2500") |
flatFee | string (decimal) | Flat per-withdrawal fee, denominated in the want asset (human-readable units) |
Error Responses
| Status | Meaning |
|---|
| 400 | Invalid parameters (bad address, non-numeric offerAmount, etc.) |
| 404 | No fee module configured for the given vaultAddress + wantAsset pair |
| 503 | Upstream RPC or indexer unavailable |
