Finding your undertone — the color under your skin, not the color of your skin — can be tricky, but TikTok user and makeup artist MAJ Beauty has shared a hack that makes it easy.

Knowing your undertone is the secret key to determining what hair colors, makeup shades, and clothing choices will look best or most harmonious with your skin.

Make a fist under neutral lighting. Yellow knuckles indicate a warm undertone, pink knuckles mean a cool undertone, and if you have a mix, your undertone is likely neutral.

If you’re still having a bit of trouble, ask a friend to do the same thing, then compare the colors to get more of a baseline idea of where you fall on the spectrum.

Other methods leave room for personal preference and can be difficult to see on darker skin tones, but the knuckle technique is precise and works on every skin color.