This is a common question among law enforcement agencies and Dale has prepared a great response:
“My advice is to forget about population versus police ratios. Some populations require more policing than others, and your ambient population may vary significantly by hour of day and day of week, or even season of year. The better measure is to forecast what the demand for service will be, usually inferred from recent historical CAD data, then calculate how many officers will be needed to handle that projected workload at the performance levels you want.
“Ops Force Deploy can do all of these calculations and many others for you. Whatever method you choose, I would say that officers/population is not at all defensible as a measure of officers required.”