Hi,
I'm working for a regional newspaper in Spain and my Excel knowledge is a bit limited.

We have an excel with Coronavirus daily cases for several geographic divisions (regions, countries...)
It follows this structure (I apologize, but the button to attach a file doesn't allow me to upload):
Place 8/3/20 9/3/20 10/3/20
Andalucía 35 54 71
Aragón 13 13 38
Asturias 7 7 28
Baleares 8 11 13

Is there a formula that can help us to discover how long does it take to [double|triple|etc] the number of cases (a growth rate)?

So, as in the small example above, in the line "Andalucía" first number of cases is "35". We want to see how many days it takes to double (8/3/20 is 35; double is 70 >> the first day that there is a number that is equal or bigger than the double is 10/3/20, so the result is 2 (days))

Or in the line "Asturias", if we want to see how long does it takes to triple, from the first day "7" it takes 2 days to do it.

I don't know if my explanation is clear. Sorry for my English.

Also, I don't know if our approach is correct.
I see in here (https://ourworldindata.org/coronavirus) that they do the calculation from the present day backwards.

Any help will be welcome.

Thanks in advance.