I have a small W-2 income and will have mostly 1099 income for 2019. I have an extra amount deducted from my W-2 income to offset my 1099 taxes. However, this year, I project to make a much higher income and need to estimate how much tax I should pay quarterly. I don't want to have underpaid when the 2019 tax season comes. I have searched the web and the IRS website trying to find a way to estimate it and it's just not very straight forward. Does anyone have a good formula for this?