My wife switched jobs from a full time W2 employee to two part time jobs (one W2 and one 1099) at the beginning of September 2016.

I am now trying to figure out how to calculate the estimated quarterly payment. With her switching jobs mid year, us filing jointly, me being a W2 employee, and her still working part time as a W2 employee, I had trouble making sense of the 1040 ES taxes form.

Please let me know if my assumptions are correct below given our numbers:

My taxable income for 2016 (W2): ~$150K

Her taxable income at her previous full time job for 2016 (W2): ~$35K

Her taxable income at her new job for 2016: ~$6K

Her income received from 1099 job in 2016: ~$12K

Given these numbers and what I have read, it seems like I should 15.3% of the $12K for social security and medicare taxes and 28% of the $12K given the tax bracket we are in. This would total 43.3% of $12K which is ~$5000.

I understand the numbers are rough and aren't exact, but is this correct conceptually? Am I missing anything?

Thanks in advance for the help!