Pipe fill

[Elec83]

Am I allowed to run 4-#12 and 6-#10 (including ground) thhn wires in a 3/4 emt?

 

[jumper]

Have you looked at the tables in Chapter 9? It gives wire and conduit areas.

Also you will probably need to derate for that many conductors. Table 310.15(B)(3)(a).

 

[texie]

Am I allowed to run 4-#12 and 6-#10 (including ground) thhn wires in a 3/4 emt?

As jumper alluded to, I think you are asking 2 questions. One, will they fit physically in a code compliant manner and second, what will be the adjusted allowed ampacity.
Off the top of my head, without doing the calculation the fill is probably not an issue. The ampacity question would need a lot more info.