I'd recommend using IRS Form 1040-ES publication. You'll see on page 8 of this publication a worksheet for calculating your estimated tax payments. But since you also have self employment income, you'll need to first complete the worksheet on page 6 before completing page 8.
It's a bit complicated, but it's the most accurate way to estimate your 2019 tax payments. I'm linking the publication below.
https://www.irs.gov/pub/irs-pdf/f1040es.pdf
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
