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Lower third of the face: measuring the balance
The lower third runs from the base of your nose to the bottom of your chin and splits at the mouth. The upper lip segment at about a third of the total, the chin segment at about two thirds, is the reference. Past roughly 40% the upper lip reads long; under about 28% the chin reads tall. The upper segment lengthens with age; the rest is bone and surgery.
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VerdictRoughly one to two
Verdict
Roughly one to twoUpper lip segment about a third of the lower third is the reference; past roughly 40% the upper lip reads long, under about 28% the chin reads tall
Do your facial analysis: Facial thirds & ratios →How the section divides
Measure from the base of the nose to the mouth opening, then from the mouth opening to the bottom of the chin. The planning convention used in surgical and orthodontic work puts the upper segment at roughly one third of the total lower third and the lower segment at roughly two thirds.
Like the facial thirds above it, this is a guideline from proportion canons rather than a measured population norm, and real faces scatter around it in both directions. Its use is locating: it tells you which half of a lower third that reads long or short is responsible, which is the first thing any specialist would want to know.
Measuring it
Straight-on photo, camera at eye height, head level, teeth lightly together, lips closed and relaxed. Mark three horizontal lines: nose base, the mouth line, and the bottom of the chin. Compare the two segments as percentages of the whole lower third rather than in absolute units, since absolute size depends on how far from the camera you stood.
Two things wreck it. A smile or a compressed lip moves the mouth line, and a lifted or dropped chin stretches or compresses the lower segment. Because the lower third is where expression lives, this measurement is more sensitive to expression than any other on this list, so repeat it on a second day before trusting it.
How much is too much, and what it costs
Between roughly 30 and 38% for the upper segment, the split goes unnoticed. Past about 40% the upper lip reads long: the philtrum stretches, the upper teeth hide when the mouth is relaxed and when speaking, and the face reads older, since upper lip lengthening is one of the consistent changes of aging. That is the common direction, and it is what lip lifts address.
Under about 28% the chin segment dominates and the chin reads tall, which from the front reads as a long face and in profile often as a heavy or forward chin. A tall chin segment that comes from the jaw sitting low usually arrives with a bite that does not meet at the front, which is an orthodontist’s question. A shift in how the teeth meet, in an adult, is a reason to see one.
What actually changes it
The upper segment lengthens with age as the upper lip descends and thins, so the balance drifts toward a long upper lip over decades with nothing skeletal changing. That is the most common reason someone measures differently than they remember. Lip filler makes the visible lip occupy more of the segment; a lip lift shortens the skin permanently by several millimeters. Both are facial plastic surgeon decisions.
The chin segment is bone and teeth. Chin height reduces with a genioplasty that removes a wedge of bone, and a low-sitting jaw is orthognathic surgery, both planned with imaging by a maxillofacial surgeon. Measure your split with the facial thirds and ratios tool; because the upper segment drifts slowly, the SkinPal app is the honest way to see it move over years rather than noticing it all at once.
FAQ
Common questions
How do you measure the lower third of the face?+
From a level, straight-on photo with the bite relaxed and lips closed, measure nose base to the mouth line and the mouth line to the bottom of the chin, then express each as a percentage of the whole lower third.
What is the ideal lower third proportion, and when is it off?+
The reference puts the upper lip segment at about a third and the chin segment at about two thirds. Between roughly 30 and 38% for the upper segment nobody notices. Past about 40% the upper lip reads long and older; under about 28% the chin reads tall and the face long.
What causes a long lower third?+
Chin height, jaw length, or the vertical position of the teeth, and often a combination. These look similar in a photo but are different findings, which is why a home measurement locates the area rather than explaining it. The split tells you which half is responsible.
Does the lower third change with age?+
Yes, gradually. The upper lip lengthens and thins over decades, which pushes the upper segment toward and past 40% even when nothing skeletal has changed. That is the drift a lip lift is designed to reverse.