RMR is an updated version to the original HB equation to accommodate a wider demographic population. Unlike BMR which is measured under very restrictive circumstances when a person is awake, but at complete rest - RMR offers a less strict measurement. Both BMR and RMR, as with all online calculators, offer only approximations and individual factors (e.g. activity level, body type, health, etc) should be considered when deciding what to target for daily caloric needs.