Largly meaningless Kim as every organisation has different roles/titles/needs etc., A bit like asking how long is a bit of string...... : -)

For what its worth my last job had over 500 staff in 26 different locations and there was me and my boss plus two admins.

Although David is absolutely correct and YMMV and all that, I have found, historically, that starting from an assumption of 1.0 FTE per 100 employees is a useful rule of thumb and you can then move that number left and right, depending on the nature of the organization and skill level of the HR staff and support systems you're prepared to pay for.

Generally, mo' staff, mo' problems. But also mo' staff, mo' budget, so you get better HRIS and higher skill staff that offsets the growth in workload that comes from larger organisations.