In my opinion, there are a lot of factors that could impact that ratio. Some of them include:
1) Productivity levels of the providers involved. Some providers see 65+ patients per day. Others max out at 20.
2) Specialty. For example, coding 20 chest xrays would be expected to be much faster than coding 20 complex orthopedic surgeries.
3) Level of coding required. Are the coders coding CPT and ICD10 from scratch? Or are they just scrubbing what the provider coded?
4) Computer systems and integration. Do the coders have to search for the op note in one system, the pathology in another, then enter the charges into a third? Expect that to take longer than one fully integrated system.
5) Other work. What other work do your coders perform? Provider education? Given continuing education time? Is your organization very meeting centric? Any billing responsibilities?
6) Work hours. I have seen full time in organizations range from 35-40 hours. Particularly once you extrapolate that to dozens of coders, 5 hours less or more per week of work per coder makes a difference.
7) Experience level. An entry level CPC-A would not be expected to be as productive as a lead coder with 10 years experience in that specialty.
To me, more than a ratio of coders to providers is to have some type of productivity expectations for your coders. For E&M services, I would expect ballpark of 10-12 per hour. In my organization for hospital E&M, I expect abut 8/hr since they need to maneuver several computer systems to do this. Surgeries about 5-6 per hour. Keeping in mind other responsibilities, allot time each day for emails, meetings, etc. I also like to keep my coders assigned to a specific specialty and/or group of providers. You can definitely build up speed when you are more familiar with common codes in a particular specialty.
I would run productivity reports on your current coding employees and then set the expectation somewhere near the middle.