It depends on the charge & whether there were any enhancements, such as great bodily injury, or weapon use.
For non-violent felonies, it's usually 50% good time/work time (the formula is actually 'divide the actual days in custody by four & times the result by two'. This isn't guaranteed - the behavior in custody will affect whether it's earned.
85% time is usu strikes & serious, violent crimes. Again, behavior of the defendant will affect good time/worktime credit. They may have to do 100%.
What was the conviction for ?