Stila/Mac translation question

[Laurahead108]

Hi,
I want to buy my sister a Mac TM as a gift, but am unsure what shade. I know she wears Stila powder foundation in 40 watts. Any ideas?

Many thanks,
laura

 

[danabanayna]

I wear 40 watts in the fluid and I'm an NW25..HTH

 

[MAC_Pixie04]

I have a question for this too: if i wear MAC NW45, what shade would I be in Stila? My Stila concealer is Shade J and it's a perfect match, but as far as the foundations (Watts etc etc) what shade would I go?