Quarterly taxes for physician independent contracting/moonlighting work

Hello, 

 

I am physician and perform independent contracting/moonlighting work in addition to my main employment role. Through my contracting work, I receive a 1099-NEC (not a W2), and as a result, have been recommended to file quarterly taxes. I am wondering how best to go about this process in terms of estimating the amount of quarterly taxes to be paid (given that the amount of contracting shifts I perform each quarter can vary). 

 

Thank you!