It depends on the province. There is a calculator at
http://www.cra-arc.gc.ca/esrvc-srvce/tx/bsnss/pdoc-eng.html First accept
On the next screen pick a province and monthly, then click on Salary / Bonus etc.
On the next screen, click on Determine gross income
Next screen write 1200 in the Salary field and click OK
Next screen, click calculate
I tried it for BC and AB, both give you around 1100 left after taxes.