So just where should you match your foundation to? Your face? Your jawline? Your neck? Your chest? HALPPPPPP!!!
My answer: all the above! Let me explain.
When you do a quick search on this topic online, it seems as though everyone has their preferred spot...but that to me is the problem! Using just one area to match your foundation will mean, well, your foundation might only really look good in that one place. If you ask me, people are far too zoomed in when they are trying to match foundation. So what should you be doing instead? Take a step back.
When I match foundation on a client, I take into account the over all skin tone that I see from basically their chest all the way up to their forehead. Because guess what? If your face is paler than your neck and upper body, you're going to look like a ghost AND have a strong line where your foundation is visible if you match your face only. Or even if you are fairly even-toned everywhere, you might get distracted by surface redness on your cheek, for example. This is what I mean by being too 'zoomed in' when you are doing a foundation match.
My recommendation is this: stand back in a mirror to where you can see your chest, shoulders, neck, and face fully. Then start to analyze foundation colors in relation to this area as a whole. I myself like to place a big splotch of foundation on the back of my hand and then hold it up next to my upper body in the mirror to see how the tones compare this way. After you hone in on a few close shades using this method, then you can proceed to testing them out on your face to see if you do have a true match once it hits your skin. Most people are skipping the first part of this process and going straight to the face, which can give you some mixed results. Have you ever noticed that foundations don't actually look exactly like real skin tones? Oftentimes the undertone of the foundation stands out drastically, and analyzing it up close might lead you to believe it will be too yellow (or too anything) until you take a step back to see how it will blend with your overall complexion. I'm telling you...this is info is going to help you out a lot! I honestly haven't seen anyone else recommend doing a foundation match this way ever. Even Sephora (no shade at all! Just something I noticed in their foundation video) is still using the '3 stripes on your jawline' method. But I'm telling you...using this method of foundation matching is how I can immediately mix up a client's perfect foundation match within seconds and it works.
As a final note, when you decide to test out a few shades on your face itself, you need to apply the foundation as you would at home--meaning it should be over a large area and it should be blended in. When I see people putting a thick, unblended stripe of foundation on their face as a 'test' I think...'There is no way they can judge how that is actually going to look once it's actuallyon!' So make sure especially that you have blended the foundation down, just like you would at home.
Hope this advice helps, y'all! Make sure you send me all of your makeup questions so I can keep posting advice for the benefit of all! :)