I have found the range calculator on the British Specialized site ( specialized.com then select region)
Have never found it elsewhere. This is EU so it only works for speeds up to 16mph.
You choose a bike model and there is a ”button” to the right under the image of selected bike.
I find the range calculator a bit optimistic when comparing it to what I managed with my Vado 4.0 last summer. I did rides in rather flat areas but not Bonneville Salt Lake flat so maybe I should select hills as terrain. That gives a result more like what I got from my battery.