Is the two fingers sunscreen method enough for your face?
Let's test it.
First, I used the free calculator I built to calculate exactly how many grams of sunscreen I need for my face and all my other body parts.
For me, it's 2.1 grams for my face and neck. Now let's measure out two fingers worth,
an amount commonly cited as enough for your face and neck. Got my handy dandy sunscreen and two messy lines. Let's scrape it onto my jewelry scale.
And we see that, even with a little bit lost in the scraping we end up with a little over one gram. That would probably give me less than half the labeled SPF.
This is why it's important to calculate before just relying on a heuristic, like the two finger method, although it's a decent start.