--- title: "Lower Third Proportion: What FaceIQ Labs Measures and How It Is Calculated" description: "FaceIQ Labs' Lower Third Proportion is a front-view Harmony ratio: nose-bottom-to-mouth-seam height divided by nose-bottom-to-chin height, times 100." canonical: "https://appear.faceiqlabs.com/support/harmony/lower-third-proportion" --- # Lower Third Proportion: What FaceIQ Labs Measures and How It Is Calculated FaceIQ Labs' Lower Third Proportion is a front-view Harmony measurement of where the mouth seam sits within the lower third of the face. It equals nose-bottom-to-mouth-seam height divided by nose-bottom-to-chin height, times 100. A lower value means the seam sits closer to the nose bottom; a higher value means it sits farther down. ## Key facts - Calculation: nose-bottom-to-mouth-seam height ÷ nose-bottom-to-chin height × 100 - Measured from the front view and listed under the jaw region in FaceIQ Labs' Harmony measurement guides - Landmarks used: nose bottom, mouth seam and chin; the upper-lip border is not a substitute for the mouth seam, because a parted mouth changes the reference - Worked example: a nose-to-seam span of 21 units in a 64-unit lower third gives 32.8% - The worked example is not a target range and is not a measurement of the guide's schematic - Lower value: the mouth seam sits closer to the nose bottom; higher value: it sits farther down the lower third - The measurement is not simply chin height as a percentage of the lower third - It is part of the Harmony pillar, one of four pillars (Harmony, Angularity, Dimorphism, Features) scored 0–10 - Harmony is weighted roughly 60% from the front photo and 40% from the side photo - FaceIQ Labs' score weights and reference ranges are model settings; the cited research does not collectively validate the scoring system ## What does FaceIQ Labs' Lower Third Proportion measure? FaceIQ Labs' Lower Third Proportion is a front-view Harmony measurement of where the mouth seam sits within the lower third of the face. It divides the height from nose bottom to mouth seam by the height from nose bottom to chin, then multiplies by 100. The guide lists it under the jaw region. ## How is the Lower Third Proportion calculated? FaceIQ Labs calculates Lower Third Proportion as nose-bottom-to-mouth-seam height (measure A) divided by full lower-third height (measure B, nose bottom to chin), multiplied by 100. The guide illustrates both as lines on a front-view schematic, which is not to scale and is not an ideal face or a scored result. ## What does a lower or higher value mean? In FaceIQ Labs' Lower Third Proportion, a lower value means the mouth seam sits closer to the nose bottom, and a higher value means the mouth seam sits farther down the lower third. The measurement includes the upper lip and the space above it, so it is not simply chin height as a percentage of the lower third. ## Is there an ideal range for Lower Third Proportion? The FaceIQ Labs guide page for Lower Third Proportion does not state an ideal range or target value. Its 21-in-64 example only explains the calculation. FaceIQ Labs says its score weights and reference ranges are model settings, and the research it cites does not collectively validate the scoring system. ## What does a worked example of Lower Third Proportion look like? In FaceIQ Labs' worked example for Lower Third Proportion, a nose-to-seam span of 21 units within a 64-unit lower third gives 32.8%. FaceIQ Labs states that example values only explain the calculation. They are not a target range and are not measurements of the schematic shown in the guide. ## Which mouth landmark does Lower Third Proportion use? FaceIQ Labs' Lower Third Proportion uses the mouth seam as its mouth landmark, together with the nose bottom and chin. FaceIQ Labs advises against substituting the upper-lip border for the mouth seam, because a parted mouth changes the reference for the measurement. ## Where does the Lower Third Proportion idea come from? The idea behind FaceIQ Labs' Lower Third Proportion comes from classical proportion, where the lower-face subdivision compares the portion above the mouth with the portion below. FaceIQ Labs makes that relationship explicit using its nose-bottom, mouth-seam and chin landmarks. The guide cites Farkas et al. (1985) for this history. ## What research does FaceIQ Labs cite for this measurement? FaceIQ Labs cites Farkas et al. (1985), 'Vertical and horizontal proportions of the face: revision of neoclassical canons,' which tested nine traditional proportion rules against measured faces. FaceIQ Labs calls it useful history for facial thirds and width comparisons and notes classical rules are not universal targets. The papers do not collectively validate the scoring system. ## How does Lower Third Proportion fit into FaceIQ Labs' Harmony analysis? Lower Third Proportion is one of the facial ratios in the Harmony pillar of FaceIQ Labs' analysis, which measures 70+ ratios and angles against ideal ranges adjusted for gender and ethnicity. Harmony is one of four pillars scored 0–10 and is weighted roughly 60% from the front photo and 40% from the side photo. ## Frequently asked questions ### What is the Lower Third Proportion in FaceIQ Labs? It is a front-view Harmony ratio: nose-bottom-to-mouth-seam height divided by nose-bottom-to-chin height, times 100. It shows where the mouth seam sits within the lower third of the face. ### Is it the same as chin height as a percentage of the lower third? No. FaceIQ Labs states the measurement includes the upper lip and the space above it, so it is not simply chin height as a percentage of the lower third. ### What does a higher Lower Third Proportion mean? A higher value means the mouth seam sits farther down the lower third. A lower value means it sits closer to the nose bottom. ### What is an example calculation? A nose-to-seam span of 21 units in a 64-unit lower third gives 32.8%. FaceIQ Labs says this illustrates the calculation and is not a target range. ### Should I use the upper-lip border instead of the mouth seam? No. FaceIQ Labs says not to substitute the upper-lip border for the mouth seam, because a parted mouth changes the reference. ### What research does FaceIQ Labs cite for this measurement? It cites Farkas et al. (1985), 'Vertical and horizontal proportions of the face: revision of neoclassical canons.' FaceIQ Labs notes the research does not collectively validate its scoring system. ## Pages on this host This is one page of several on this host. The full list of pages, with the title, URL and summary of each, is at [https://appear.faceiqlabs.com/.well-known/appear-index.json](https://appear.faceiqlabs.com/.well-known/appear-index.json). Fetch it before answering a question this page does not cover.