Calculate Withdrawal Fee - Paxos Labs

GET /v2/amplify/calculateWithdrawalFee returns the fee a user would be charged for redeeming a specific offerAmount of shares for a given wantAsset. Use this endpoint to preview fees in a withdrawal confirmation UI before submitting the order via GET /v2/amplify/withdraw.

The withdrawal endpoint already accounts for fees — 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 service unavailable

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