USDC and USDT both aim to be worth one US dollar, so their market rate against each other usually sits very close to 1.00. A swap, however, is almost never exactly 1:1. What you receive is the market rate minus the service margin and minus the network fee for the payout, and on a small amount the network fee dominates. On a large amount, tiny deviations of the market price from 1.00 start to matter as well.
Why the market rate is close to, but not exactly, 1.00
The two coins are issued by different companies, Circle and Tether, with different reserves, redemption rules and user bases. Large holders can redeem them with the issuer for dollars, which keeps both near the peg, but demand still moves in waves. During market stress traders sometimes prefer one over the other, and the USDC/USDT price drifts a few hundredths of a percent, occasionally more.
The clearest example is March 2023. After Circle disclosed that $3.3 billion of USDC reserves were held at the failed Silicon Valley Bank, USDC traded as low as about $0.87 to $0.88 on 11 March, according to CNBC and The Block, and then recovered after Circle said it would stand behind the peg. Episodes like that are rare, but they show that 1:1 is a target, not a guarantee.
What makes up the amount you receive
| Component | What it is | Depends on |
|---|---|---|
| Market rate | USDC/USDT price on liquid markets | Demand for each coin; normally within a fraction of a percent of 1.00 |
| Service margin | The swap service or exchange fee | The platform; on KOT.CASH it is built into the rate shown |
| Payout network fee | Cost of sending USDT to your address | The USDT network you choose: ERC20, TRC20, BEP20, Solana and so on |
| Your sending fee | Gas you pay to send USDC | The network your USDC is on |
| Exchange withdrawal fee | If you send from an exchange account | That exchange's fee table |
The first three are all included in the receive estimate on a swap form. The last two you pay separately, outside the swap. To see how a quoted rate compares with the market, plug both numbers into the rate markup calculator.
A worked example with round numbers
Assume a market rate of exactly 1.0000 to keep the arithmetic visible, and take an imaginary service margin of 0.5% and a payout fee of 1 USDT. These are not KOT.CASH figures; the live estimate in the form is what counts. The point is the shape of the result.
| You send | After a 0.5% margin | After a 1 USDT payout fee | Effective rate |
|---|---|---|---|
| 50 USDC | 49.75 | 48.75 USDT | 0.975 |
| 500 USDC | 497.50 | 496.50 USDT | 0.993 |
| 5,000 USDC | 4,975.00 | 4,974.00 USDT | 0.9948 |
The fixed network fee is what pushes small swaps furthest from 1:1. Choosing a cheaper payout network is often a bigger saving than hunting for a better rate. The stablecoin fee comparison lists typical transfer costs by network, and the swap fee calculator lets you test your own numbers.
How to get as close to 1:1 as possible
- Decide where the USDT has to go and pick that network first; a second transfer later costs another network fee.
- Send USDC from a self-custody wallet on a cheap network if you can, rather than from Ethereum mainnet.
- Compare the final receive amount, not the advertised rate or fee percentage.
- Avoid splitting one swap into many small ones: each payout pays the network fee again.
- For large amounts, check the current USDC/USDT market price; during stress the gap can be larger than the fee.
Same network or cross-network
Swapping USDC on Ethereum to USDT on Ethereum and swapping USDC on Base to USDT on TRON are the same operation for you: send one coin, receive the other. The difference is which networks pay which fees. Cross-network swaps also save you a separate bridge step. Use the USDC to USDT pair for the forward direction and USDT to USDC for the reverse; if your USDC is on Base, our USDC on Base guide covers the specifics.
Should you swap at all
This article does not recommend one stablecoin over the other. The usual practical reasons are acceptance: a recipient, exchange or app supports only one of them, or only one on the network you need. Both carry issuer risk and can be frozen at specific addresses by their issuers under their own policies. If neither of those reasons applies, staying in the coin you already hold avoids paying the spread at all.
FAQ
Is USDC to USDT always 1:1?
No. Both target $1, so the market rate is usually very close to 1.00, but a swap also deducts a service margin and the payout network fee. In rare stress events the market rate itself has moved noticeably away from 1.00.
Why did I receive less USDT than the USDC I sent?
The difference is usually the service margin plus the network fee for sending USDT to you. On small amounts the fixed network fee is the largest part.
Which network is cheapest for USDC to USDT?
It depends on where your USDC is and where the USDT has to go. Ethereum mainnet is generally the most expensive; TRON, BNB Smart Chain, Solana and L2 networks are usually much cheaper.
Has USDC ever lost its peg?
Yes. On 11 March 2023, after Circle disclosed $3.3 billion of reserves at Silicon Valley Bank, USDC traded as low as roughly $0.87–0.88 before recovering.