Convert USDT and USDC

Preview the price, then convert USDT to USDC or back between two wallets of the same customer.

Use this recipe to preview the price, then convert USDT to USDC, or USDC to USDT, between two wallets of the same customer.

Who it is for. A treasury app whose customer received USDT on Ethereum but needs USDC on Polygon to pay suppliers.

Status. Available between two wallets of the same customer. No conversion has completed in production yet, so always preview the price first. Gravv does not support Tron. You cannot convert and send to someone else in one call. Convert first, then send.

Money example

1. The customer converts 2.00 USDC in a Polygon wallet into USDT in their Ethereum wallet.
2. The preview shows a fee of 1.501737 USDC and a receive amount of 0.498263 USDT.
3. 2.00 USDC leaves the Polygon wallet, and about 0.498 USDT arrives. The fee comes out of the amount that arrives. Gravv never charges it on top.
4. Part of the fee works like a fixed cost, so preview the price first and convert larger amounts.

Before you start

• Both wallets are Gravv wallets (internal_crypto_wallet) of the same customer, and that customer is the customer_id you send (GET /v1/wallets/{wallet_id} shows customer_id).
• The source wallet holds the asset you send.
• The amount has at most 2 decimal places.

Find out what is required

Get a price first with GET /v1/transfer/rates in preview mode. A preview reserves and charges nothing.

curl --request GET \
 --url 'https://api.gravv.xyz/v1/transfer/rates?source_wallet_id=b6705e3a-3c6c-49b0-b24f-d55aafd03635&destination_wallet_id=5485cc5d-3d4b-4b17-9033-95e408405f03&send_asset=USDC&receive_asset=USDT&amount=2.00' \
 --header 'Api-Key: <API_KEY>'

const response = await fetch("https://api.gravv.xyz/v1/transfer/rates?source_wallet_id=b6705e3a-3c6c-49b0-b24f-d55aafd03635&destination_wallet_id=5485cc5d-3d4b-4b17-9033-95e408405f03&send_asset=USDC&receive_asset=USDT&amount=2.00", {
method: "GET",
headers: {
"Api-Key": process.env.GRAVV_API_KEY,
},
});
console.log(response.status, await response.json());

import os

import requests

response = requests.get(
"https://api.gravv.xyz/v1/transfer/rates?source_wallet_id=b6705e3a-3c6c-49b0-b24f-d55aafd03635&destination_wallet_id=5485cc5d-3d4b-4b17-9033-95e408405f03&send_asset=USDC&receive_asset=USDT&amount=2.00",
headers={
    "Api-Key": os.environ["GRAVV_API_KEY"],
},
)
print(response.status_code, response.json())

{
  "data": {
    "items": [
      {
        "currency_pair": "USDC_USDT",
        "from_currency": "USDC",
        "to_currency": "USDT",
        "rate": "0.249132",
        "direction": "USDC_USDT",
        "timestamp": "2026-10-12T13:40:00Z",
        "send_amount": "2",
        "fee": "1.501737",
        "fee_currency": "USDC",
        "receive_amount": "0.498263",
        "min_receive_amount": "0.498263",
        "source_network": "polygon",
        "destination_network": "ethereum",
        "expires_at": "2026-10-12T13:41:00Z"
      }
    ]
  },
  "error": null
}

receive_amount is the amount that should arrive, and min_receive_amount is the lowest amount that can arrive. fee is in the asset you send. The preview is not binding. Gravv fetches the price again when you send the transfer.

Steps

1. Convert

Send a transfer whose destination.crypto_asset differs from the asset you send. That difference makes the transfer a conversion.

curl --request POST \
 --url https://api.gravv.xyz/v1/transfer \
 --header 'Api-Key: <API_KEY>' \
 --header 'Content-Type: application/json' \
 --header 'Idempotency-Key: 335c34c9-1739-428f-9bcc-478645b1c8e5' \
 --data '
{
"customer_id": "c7ae0522-6a4d-476f-a43c-5a9aac863c31",
"source": {
"source_type": "internal_crypto_wallet",
"id": "b6705e3a-3c6c-49b0-b24f-d55aafd03635",
"crypto_asset": "USDC"
},
"destination": {
"destination_type": "internal_crypto_wallet",
"id": "5485cc5d-3d4b-4b17-9033-95e408405f03",
"crypto_asset": "USDT"
},
"amount": "2.00",
"description": "Convert USDC to USDT"
}
'

const response = await fetch("https://api.gravv.xyz/v1/transfer", {
method: "POST",
headers: {
"Api-Key": process.env.GRAVV_API_KEY,
"Content-Type": "application/json",
"Idempotency-Key": "335c34c9-1739-428f-9bcc-478645b1c8e5",
},
body: JSON.stringify({
"customer_id": "c7ae0522-6a4d-476f-a43c-5a9aac863c31",
"source": {
  "source_type": "internal_crypto_wallet",
  "id": "b6705e3a-3c6c-49b0-b24f-d55aafd03635",
  "crypto_asset": "USDC"
},
"destination": {
  "destination_type": "internal_crypto_wallet",
  "id": "5485cc5d-3d4b-4b17-9033-95e408405f03",
  "crypto_asset": "USDT"
},
"amount": "2.00",
"description": "Convert USDC to USDT"
}),
});
console.log(response.status, await response.json());

import os

import requests

response = requests.post(
"https://api.gravv.xyz/v1/transfer",
headers={
    "Api-Key": os.environ["GRAVV_API_KEY"],
    "Content-Type": "application/json",
    "Idempotency-Key": "335c34c9-1739-428f-9bcc-478645b1c8e5",
},
json={
    "customer_id": "c7ae0522-6a4d-476f-a43c-5a9aac863c31",
    "source": {
        "source_type": "internal_crypto_wallet",
        "id": "b6705e3a-3c6c-49b0-b24f-d55aafd03635",
        "crypto_asset": "USDC",
    },
    "destination": {
        "destination_type": "internal_crypto_wallet",
        "id": "5485cc5d-3d4b-4b17-9033-95e408405f03",
        "crypto_asset": "USDT",
    },
    "amount": "2.00",
    "description": "Convert USDC to USDT",
},
)
print(response.status_code, response.json())

{
  "data": {
    "amount": "2",
    "amount_currency": "USDC",
    "reference": "f3a9c1d7-2b4e-4c6a-9d8f-0e1b2c3d4e5f",
    "date_created": "2026-10-12T13:42:10.000Z",
    "transfer_status": "pending",
    "transaction_id": "a7c3e9f1-4d2b-4a8c-b6e0-1f2a3b4c5d6e",
    "local_amount": null,
    "local_currency": null,
    "fee": "1.501737",
    "fee_currency": "USDC",
    "requires_approval": false,
    "receive_amount": "0.498263",
    "min_receive_amount": "0.498263",
    "receive_asset": "USDT"
  },
  "error": null
}

Compare receive_amount with the preview, and check that it is still acceptable to you.

2. Wait for it

Wait for the transfer.status.completed webhook. It gives the amount that arrived (receive_amount) and the amount the converter kept (provider_fee). As a backup, poll GET /v1/transactions/a7c3e9f1-4d2b-4a8c-b6e0-1f2a3b4c5d6e.

The transaction shows no fee for a conversion. You find the fee in the transfer response and the webhooks.

3. Pay out

Send the converted funds from the receiving wallet as in Send stablecoins to an outside wallet.

What can go wrong

Webhooks you will receive

1. transfer.status.pending, with workflow_type stablecoin_conversion. Its event_data carries send_asset, amount_sent, receive_asset, receive_amount, min_receive_amount and provider_fee.
2. Then one of these:
   • transfer.status.completed, with the actual receive_amount and provider_fee.
   • transfer.status.failed, with refunded_amount and refund_asset.

Testing in sandbox

You cannot test a conversion in sandbox. There is no test converter, so both the preview and the conversion return We couldn't get a price right now. Please try again shortly.

The request checks still run first. So in sandbox you can still see receive_asset must differ from the asset sent., Use at most 2 decimal places. and the same-customer error.

Reference

• Get rates
• Create a transfer
• Crypto transfers