You’ve probably heard that you need 1/4 teaspoon of sunscreen to cover your face. This quantity is calculated from an estimate of people’s face sizes, and the amount of sunscreen they use in SPF testing (2 mg per cm2). Since it’s based on the thickness of sunscreen, a larger face will need more sunscreen, while a smaller face will need less sunscreen. But how much sunscreen would I need?
Because I have an unusually large forehead and a flat-but-wide nose, I didn’t want to use a rough geometric estimate, and opted for a more empirical (and hopefully accurate), fiddlier measurement method instead. I decided to work out my facial surface area by covering my face with paper tape, then taping it onto grid paper and counting the area. Of course, I filmed the process! I then worked out how much sunscreen I needed for my face, and I also worked out how much sunscreen I needed for my neck and decolletage.
Here’s the video:
The materials I used:
- Paper tape: I used a generic version of 3M Micropore
- Grid paper: I used a grid spacing of 0.5 cm and heavier lines of “2”
Here are the other estimates that people have come up with (different people have different faces, so these may not be relevant to your situation – when in doubt go with the full 1/4 tsp):
- SCCS (EU): 25th percentile of women’s faces (half head) = 565 cm2 (I made a mistake here in the video, sorry – it was a Dutch study, not a Danish study!)
- John (Futurederm): Rectangular estimate = 620 cm2
- Korean TV show (I can’t find the link anymore unfortunately, let me know if you have it!): Grid sticker overlaid on male face = 400 cm2
- Reddit (/u/avecsagesse): Divided face into rectangular zones = 364.5 cm2
- Reddit (/u/littlepinkkitty): Estimated face as an oval = 362 cm2
Related post: How SPF Changes With How Much Sunscreen You Use
Here’s what my grid looked like after I stuck all the tape down, with all my working for counting the squares:
Here are my measurements, and the conversions to 1/4 teaspoon amounts:
Edit: Out of curiosity, I also tried estimating my face as an ellipse and as a circle to compare with the numbers I got from the tape method:
- Face height: 20.5 cm
- Face width: 26 cm
- Estimate as an ellipse (A = πab): 418.62 cm2 (9.9% difference)
- Estimate as a circle (estimate radius as the average of the two axes, A = πr2): 424.56 cm2 (11.4% difference)
The accuracy of this method depends on how protruding your features are, but it isn’t a bad estimate if you don’t want to spend 40 minutes applying tape to your face.
Official sunscreen usage recommendations:
Related post: Video: All Your Sunscreen and Makeup Questions Answered
Density of mineral sunscreen: PG McCormick, Adapting SPF testing methods for mineral sunscreen density, Cosmetics & Toiletries 2011, 164.
Paper tape was a press sample I got at a media event. This post contains affiliate links – if you decide to click through and support Lab Muffin financially (at no extra cost to you), thank you! For more information, see Disclosure Policy.