How to Find Your Undertone

Set up first, because the setup is most of the accuracy

• Daylight, near a window, in the middle of the day. Indoor bulbs are warm and will push every result warm. Do not use a bathroom mirror with overhead lights.
• No makeup, including tinted moisturiser. Foundation is chosen to flatter, so it hides exactly the signal you are looking for.
• Hair pulled back and covered with a neutral grey or white towel, especially if it is dyed.
• Wear something neutral, or drape a white towel over your shoulders. A saturated top will bounce colour onto your neck and change the reading.

Test 1: pure white against ivory

This is the most reliable single test and it is the one professional analysts start with. Hold pure white fabric under your chin, look at the skin under your eyes for ten seconds, then swap to ivory or cream and look again.

Cool skin against pure white looks clean and the shadows soften. Warm skin against pure white can look faintly grey or sallow, and then settles when the ivory goes up. What you are watching for is the shadows and the evenness of your skin, not whether you like the fabric.

Test 2: gold against silver

Hold a gold item and then a silver one flat against your bare cheek or on your jaw. The reliable read is whether the metal blends into your skin or sits on top of it. Gold on warm skin looks continuous with it; silver on warm skin looks like an object.

This test is confounded for the Bright seasons, who often genuinely suit both because their defining feature is clarity rather than temperature. If both metals look fine to you, treat that as evidence about your chroma rather than a failed test.

Test 3: which pink and which green

Two pairs of colours, held up the same way. Coral or salmon pink against a cool blue based pink. Then olive against a clear emerald.

Warm skin holds up against coral and olive; cool skin holds up against blue pink and emerald. This test is useful precisely because it does not depend on you owning fabric samples: two shirts from your wardrobe will do.

Test 4: the photograph

Take a bare faced photo in indirect daylight with the flash off and look at it on a screen you have not colour tweaked. Photographs are useful because they remove the wishful thinking a mirror encourages, and because you can compare two shots side by side rather than from memory. This is also what the tool on this site does, with the added step of correcting for the light's colour cast before it measures.

The vein test does not work

The most repeated undertone test on the internet asks you to look at the veins on your inner wrist and decide whether they look blue (cool) or green (warm). It does not measure undertone.

What you are seeing is light scattering. Blood in veins is dark red. The blue or green appearance is produced by how skin scatters and absorbs light at different wavelengths, together with how deep and how wide the vessel is; Kienle and colleagues worked the optics out in Applied Optics in 1996 and the answer had nothing to do with the colour of the blood. Because the effect depends on the tissue above the vessel, the test partly measures how thick and how pigmented your skin is, which is the exact thing undertone is supposed to be independent of, and it is least informative for the deeper skin tones where the veins are hardest to see at all.

The sun reaction test, burn means cool and tan means warm, has the same problem in a different form. It is the Fitzpatrick scale, and Fitzpatrick's own 1988 paper says what it was built for: choosing starting doses of ultraviolet light for psoriasis phototherapy in white skin. It measures how skin responds to UV, which is a melanin question. A 2025 study in npj Digital Medicine put a number on the gap: predicting someone's Fitzpatrick type from an objective colour measurement of their face was right about 20% of the time.