How much is a USDT to BTC fee?

I'm curious to know, when it comes to converting USDT to BTC, what kind of fee am I looking at? Is the fee a fixed amount or does it vary depending on certain factors? Is there a way to minimize or even avoid these fees altogether? And lastly, are there any other important considerations I should keep in mind when making this type of transaction? I'd appreciate any insight you can provide on this matter.