Converting Fiat to USDC on Polygon: A Step-by-Step Guide

May 29th, 2022

Step 0: Pre-requisites

Custodial wallet (i.e. Coinbase)
Decentralized wallet (i.e. Metamask)

Go sign up for Coinbase if you don’t have an account already - you will buy crypto with a credit card and send it to the right place.

Download Metamask and read through this article to get acquainted.

Step 0.5: Add Polygon to your Metamask

Whether you’re new to Metamask or not, you may need to add the Polygon blockchain to your wallet. Go to Polygonscan and click “Add Polygon Network” in the footer.

Click “Approve” in your wallet to add your Polygon-specific wallet. Metamask will prompt you to “Change Networks” which you may do, and instead of “Ethereum Mainnet” as in the image below, you should see either “Matic Mainnet” or “Polygon Mainnet”. Your wallet can now use and store assets on the Polygon network.

Switch back to “Ethereum Mainnet” for now. You will be transferring assets from one network to another in Step 3, originating from Ethereum.

Step 1: Buy MATIC on a Centralized Exchange

After you’ve created a Coinbase account, you’ll need to connect a bank account and/or credit card to purchase crypto. The reason you’re buying MATIC (Polygon token) from the get-go, and not USDC, is to avoid excess fees and repeat transactions.

When you buy MATIC on a platform like Coinbase, your crypto is stored in what’s called a custodial wallet. This means a third party, in this case Coinbase, has “custody” of your crypto, i.e. they hold the private keys which allow you to execute transactions and can help you recover your account if you forget the password.

Go ahead and buy MATIC using USD by clicking the blue “Buy/Sell” button. Specify that you’re buying MATIC and how much you’d like to buy, in US Dollars. We recommend also buying some Ether for gas (transaction) fees, important in Step 3.

Step 2: Sending MATIC to a Decentralized Wallet

A non-custodial (decentralized) crypto wallet is the key to your digital assets, identity, and currency in web3. Unlike a physical wallet, it doesn’t actually store anything but allows you to access web3 sites and interact with various public blockchains and smart contracts.

Since transactions require transaction (”gas”) fees to execute, you will need some extra crypto in your wallet to make sure your upcoming transactions go through without a hitch. In addition to MATIC, it is wise to purchase some Ether as well, for Ethereum network fees in the next step.

Send your MATIC and Ether to your Metamask wallet by clicking the “Send/Receive” button. Again, you’ll need to specify that you’re sending a specifc token, and to whom (wallet address).

Your wallet’s address can be found under “Account 1”—it’s the 42-character public key that begins with 0x. Copy that directly and paste into Coinbase to avoid sending money to the wrong address. IMPORTANT: double-check the address is correct. Once a transaction is sent, it cannot be undone.

After a minute or two, check the “Assets” tab in your Metamask to see that you’ve received your MATIC and Ether.

Step 3: Bridge MATIC from Ethereum Mainnet to Polygon Network

Since transferring crypto from a custodial (Coinbase) to a non-custodial (Metamask) wallet by default delivers to the Ethereum network, you will need to “bridge” your crypto from one blockchain to another, and make it usable on that blockchain’s network.

Bridging is required because MATIC stored on the Ethereum network is not usable by applications on Polygon and vice versa. Fundamental Labs wrote a great article recently on cross-chain bridges, but this is a rabbithole we won’t go down for now.

In TeamDiff’s case, our dApp is built on Polygon, meaning you’ll need MATIC in your Polygon wallet to interact with the Polygon network (and its fees). To transfer your MATIC assets to Polygon, we’ll need to use that bit of Ethereum you purchased to execute an Ethereum→Polygon bridge.

Navigate to Polygon’s Bridge and connect your Metamask wallet by clicking “sign” when prompted.

Polygon's bridge, after a wallet is connected

Select the token you plan to bridge - in our case MATIC. There will be a small Ethereum transaction fee. Wait for gas fees to be low on Ethereum network (anything below 20 gwei is solid right now), then click “Transfer” and approve the transaction from Metamask.

In about 7 or 8 minutes, the MATIC you just bridged should appear in the “Assets” tab in your Polygon wallet. Congrats! Now you have assets on Polygon, and can interact with Polygon dApps.

Step 4: Convert MATIC to USDC

Now that you have MATIC tokens on Polygon, you can convert them to whatever you need, using Metamask’s built-in swap feature. Remember to keep a few MATIC tokens handy in your Polygon wallet for gas fees. Keeping 5-10 tokens available is sufficient.

Select “swap” on Polygon Mainnet and specify MATIC→USDC. Metamask will quote you a gas fee (in MATIC) to execute the transaction. Since we’re converting to USDC in the final step rather than the beginning, we avoid paying extra Ethereum gas fees. Executing this conversion on Polygon instead is considerably cheaper.

Once you’ve approved this transaction, check your “Assets” tab and you should see a USDC balance. Now you’re ready to join a league and stake your USDC tokens.