Skin tone ITA.

Worked example

Hex #D8A48F converts to CIELAB L* about 71.6, a* about 16.3, b* about 18.3. ITA = arctan((71.6 - 50) / 18.3) = about 50 degrees, which falls in the light category (41 to 55). The hue angle atan2(b*, a*) is about 48 degrees, a pink-leaning reading.

How it works

Convert sRGB to CIELAB (D65), then ITA = arctan((L* - 50) / b*) x 180 / pi. Categories from the dermatology and cosmetic-science literature: very light above 55, light 41 to 55, intermediate 28 to 41, tan 10 to 28, brown -30 to 10, dark below -30. The foundation depth label maps each category to the usual shade-range wording.

Undertone hint: the CIELAB hue angle atan2(b*, a*). Below 55 degrees reads pink or red leaning, 55 to 65 balanced, above 65 yellow leaning. These cut points are a rough convention for this tool.

What this is not. ITA is defined for colorimeter measurements of skin. A hex from a photo or screen includes the camera, lighting and display, and the result can shift a whole category. Brands name shades differently, so use it to narrow the range, then test swatches on your jawline in daylight. For the Monk scale see the hex to Monk converter and for a vein and jewellery check see the undertone test.

Sources and basis: Chardon A, Cretois I, Hourseau C, Skin colour typology and suntanning pathways, Int J Cosmet Sci 1991;13(4):191-208 (ITA definition); Del Bino S and Bernerd F, Variations in skin colour and the biological consequences of ultraviolet radiation exposure, Br J Dermatol 2013;169(Suppl 3):33-40 (category cut points); CIE 1976 L*a*b* and the sRGB specification (IEC 61966-2-1).

FAQ

What is the Individual Typology Angle?

ITA is an angle computed from skin lightness (L*) and yellowness (b*) in CIELAB colour space. Higher angles mean lighter skin and lower angles mean darker skin. It is used in skin-colour research and cosmetics.

What ITA is light skin?

Above 55 degrees is very light, 41 to 55 light, 28 to 41 intermediate, 10 to 28 tan, -30 to 10 brown, and below -30 dark.

Can I find my foundation shade from a hex code?

It narrows the depth range, nothing more. Shade names vary by brand and screens and cameras shift colour. Swatch two or three candidates along the jaw in daylight.

How do I know if I have a warm or cool undertone?

A hex from a photo is a weak signal. Combine it with how skin looks in natural light, vein colour and whether silver or gold suits you, or use the undertone test.

Is ITA the same as the Fitzpatrick type?

No. ITA measures colour. Fitzpatrick types describe how skin reacts to sun, which also depends on how it burns and tans.