Canthal tilt: what it is and how it’s measured
Canthal tilt is the angle of the line running from the inner corner of the eye to the outer corner, measured in degrees from horizontal. When the outer corner sits higher, the tilt is called positive; when it sits lower, negative; when level, neutral. It describes eye shape rather than grading it, and head tilt, camera height and expression all change it.
What canthal tilt means
The canthi are the two corners of the eye, where the upper and lower eyelids meet. The inner corner, next to the nose, is the medial canthus; the outer corner, toward the temple, is the lateral canthus. Canthal tilt is the angle of an imaginary line drawn from the inner corner to the outer corner, compared with a horizontal line across the face.
Each eye has its own tilt, and the two rarely match exactly. The angle is usually given in degrees, with the sign telling you which way the line slopes. Because the eye is small, the corners are only a few millimeters apart vertically even when the slope is clearly visible, which is part of why the measurement is so easy to disturb.
Canthal tilt is one line through a feature that has many others. How an eye reads in a photo also depends on the upper eyelid crease, how much lid shows, the position and shape of the brow, the fullness of the cheek below and the lashes. The glossary defines the related terms, such as eye spacing and intercanthal distance.
Positive, neutral and negative tilt
| Direction | Where the outer corner sits | How it tends to read in a photo |
|---|---|---|
| Positive | Above the inner corner | The eye line slopes upward toward the temple |
| Neutral | Level with the inner corner | The eye line looks roughly horizontal |
| Negative | Below the inner corner | The eye line slopes downward toward the temple |
These are descriptions of direction, nothing more. Online communities often regard positive tilt as desirable; there is no single correct value, and the measurement is very sensitive to head tilt, camera height and expression. A tilt that reads negative in one photo can read neutral in the next simply because the head rolled a few degrees or the camera moved.
Canthal tilt is a fixed trait set by bone and soft tissue around the eye. It is a finding about your face, not something that needs changing.
How to measure canthal tilt from a photo
- Take a level photo. Hold the camera at eye level, an arm’s length or more away, with your head straight, your expression relaxed and your eyes comfortably open. Remove glasses.
- Zoom in and mark the inner corners. On each eye, place a point exactly where the upper and lower lids meet beside the nose, not on the pink tissue inside the corner.
- Mark the outer corners. Place a point where the lids meet at the outer edge of each eye. Ignore eyeliner wings and lashes, which extend past the real corner.
- Draw your horizontal. Use the line through the two inner corners as horizontal instead of the edge of the photo. This cancels most of the error from a head that is rolled to one side.
- Measure each eye separately. Find the angle between each inner-to-outer line and your horizontal. Outer corner above the line is positive; below is negative.
- Repeat on a second photo. Take another picture with the same setup and measure again. Any difference between the two is measurement noise, not a change in your eyes.
A free angle-measuring app or any image editor with a protractor tool is enough. For setup that keeps photos comparable from one session to the next, see how to take face scan photos.
Why the number moves between photos
- Head roll. Tipping your head toward one shoulder adds tilt to one eye and removes it from the other. Measuring against the inner-corner line helps, but only partly.
- Head pitch and camera height. A camera above eye level, or a chin tipped down, changes the apparent slope of both eye lines because the eye sits on a curved surface.
- Expression. Smiling pushes the lower lids up, squinting narrows the eye, and raised brows lift the outer upper lid. Each moves the visible corners.
- Lens distance. A wide-angle phone lens held close to the face exaggerates curvature at the sides of the face, where the outer corners sit.
- Point placement. The corners are small, soft-edged areas rather than sharp points. Moving a marker by a few pixels changes the angle noticeably, and two people marking the same photo will rarely agree exactly.
- Makeup. Eyeliner, a winged line or lash extensions change where the corner appears to be without changing the eye itself.
This sensitivity is why a single photo, or a single number, says little on its own. If two careful photos disagree, the honest reading is the range between them.
What MaxxLook measures instead
MaxxLook does not report canthal tilt. Of the 170+ measurements it computes, the closest is eye-region tilt: the angle between the outermost points of each eye region in the 478-point face mesh, with the iris and surrounding points included. It is reported as a magnitude only, without a positive or negative sign, so it cannot tell you which way your eyes slope. It is a proxy, not the inner-to-outer corner angle described above.
| Canthal tilt (by hand) | MaxxLook eye-region tilt | |
|---|---|---|
| Points used | The inner and outer eye corners | The outermost points of the eye region, iris included |
| Direction | Positive, neutral or negative | Magnitude only, no direction |
| Photo | Any straight-on photo you choose | The front photo of a scan |
| Read against | Nothing, unless you pick a source | Reference ranges from the same pipeline run over the FairFace image collection |
MaxxLook also compares the left and right eye-region tilt as part of its symmetry readings, and reads each one against reference ranges. The transparency page explains where those reference ranges come from, and a re-scan that moves less than the test’s noise floor is reported as “within noise”.
Can canthal tilt change?
The corners of the eye are anchored by ligaments to bone, so the underlying tilt is stable in adults and shifts slowly, if at all, over years. What changes day to day is how the eye area reads in a photo: brow grooming, eyeliner placement, sleep, and the camera angle. Those are styling and photography choices, and MaxxLook frames them as low-cost experiments rather than as corrections.
If you want to see how level your features sit overall, the free symmetry checker runs in your browser, and the facial symmetry guide explains what left and right differences mean.
Common questions
Is positive canthal tilt better than negative?
No direction is better. Online communities often regard positive canthal tilt as desirable; there is no single correct value, and the measurement is very sensitive to head tilt, camera height and expression. Canthal tilt describes the slope of the eye line, and it is one of many things that shape how an eye reads in a photo.
Does MaxxLook measure canthal tilt?
Not directly. MaxxLook measures eye-region tilt, the angle between the outermost points of each eye region in its face mesh with the iris included, from the front photo. It reports the size of that angle without a positive or negative sign, so it is a proxy rather than the inner-to-outer corner angle.
Why do my two eyes measure a different canthal tilt?
Small differences between the left and right eye are normal, and a head rolled slightly toward one shoulder adds tilt to one eye while removing it from the other. Measure against the line through both inner corners and compare two photos before reading anything into a difference.