A very rough estimate for the 0C level, too rough to be of much use 95% of the time (but don't tell your instructor
) is to take the surface temperature and subtract 2C for every 1000ft until you get to 0C so if e.g. sfc=+10C then you would expect 0C to be at 5000ft.
But as I say this is way off on many days; the other day I took off at +13C and at 6500ft it was +14C. That was at 150kt TAS so the actual temp was around +12C to +13C. That's what you call an inversion.
You can find the 0C level on F214 and F215, as well as on many other weather data sources on the www.
Clboy: I am not sure what a "single" has to do with this
Do two engines protect you from airframe icing?