Part line widening is the most common early sign of female pattern hair loss, affecting 40% of women by age 50. It is also an underutilized tracking metric for men with diffuse thinning. Your part line is a natural window into the density of your central scalp, and photographing it consistently over time reveals changes that are invisible in the mirror until they become advanced. A part that widens by just 1 to 2 mm over six months is a meaningful signal, and it is entirely detectable with a phone camera.
Why the Part Line Matters
When you part your hair, you create a visible gap that exposes the scalp beneath. The width of this gap depends directly on the density of the hair on either side of it. In a dense head of hair, the part appears as a thin, crisp line because closely packed hairs overlap to cover the scalp. As density decreases, the gap widens because fewer hairs are available to bridge across it.
This makes the part line a natural, built-in measurement tool for central scalp density. You do not need special equipment to see it. You just need to photograph it consistently.
Part Width and the Ludwig Scale
In female pattern hair loss, part line widening is the primary clinical sign used for staging:
| Ludwig Stage | Part Appearance | Density Loss |
|---|---|---|
| Stage 1 (Mild) | Slight widening, barely noticeable | Minimal density reduction along the part |
| Stage 2 (Moderate) | Noticeable widening, scalp clearly visible | Moderate density loss across the central scalp |
| Stage 3 (Severe) | Wide part, near-complete scalp visibility | Significant density loss, thin coverage |
For the full classification system, see our Ludwig scale guide for women.
In men, part widening is not part of the Norwood scale (which focuses on frontal recession and vertex thinning), but it often accompanies diffuse thinning patterns. Tracking the part line in addition to standard Norwood zone photos gives a more complete picture.
The Part Line Photo Technique
Step 1: Create a Consistent Part
Always part your hair in the same location and direction for tracking photos. Your natural part (the one you wear daily) is the best choice because it has been established over years of use and is easy to replicate.
To ensure consistency:
- Use a fine-tooth comb to create the part
- Start from the same point at the frontal hairline each time
- Follow the same line straight back toward the crown
- Part to the same side each session
If you do not have a defined daily part, choose a center part for tracking purposes. Center parts provide the most symmetrical density comparison.
Step 2: Position the Camera
Hold the camera 20 to 30 cm directly above the part line, pointing straight down. At this distance, you should capture:
- The part line running from front to back
- Approximately 3 to 5 cm of hair on each side of the part
- Enough scalp visibility to assess the gap width
If your hair is long and the full part is not visible in a single frame, take 2 to 3 overlapping photos: one of the frontal section, one of the mid-scalp section, and one of the section approaching the crown. Label them by position.
Step 3: Lighting for Part Photos
Overhead lighting is essential for part line photos. Light from above illuminates the scalp through the part evenly, without casting shadows from the hair on either side.
Position your ring light or dedicated lamp directly above, pointing straight down. This is the same lighting position used for top-of-head and crown photos. If you are capturing all three in the same session (recommended), you do not need to reposition the light.
Avoid:
- Side lighting (creates a shadow on one side of the part, making it appear narrower)
- Front-facing light (does not illuminate the scalp through the part adequately)
- Natural light (changes too much between sessions)
Step 4: Capture and Verify
Take 3 photos per section. Between shots, do not re-part the hair; just slightly adjust camera position to account for minor framing differences.
Verify each photo by zooming to 100%:
- Is the part line in sharp focus?
- Can you see individual hairs along the part edge?
- Is the scalp visible and evenly lit through the gap?
- Is the framing similar to your previous session?
Measuring Part Width
The Visual Comparison Method
The simplest approach is a side-by-side visual comparison of monthly photos. Open this month's photo next to last month's in your phone gallery and compare the width of the visible scalp gap at the same position along the part. Over 3 to 6 months, widening becomes apparent even without precise measurement.
The Ruler Reference Method
For quantitative tracking, place a small ruler or measuring tape perpendicular to the part line in the photo. This provides a calibrated reference that lets you measure the actual width of the part in millimeters. Even 1 mm of widening over 6 months is detectable with this method.
The Pixel Count Method
If you take photos at a consistent distance with a consistent camera, you can measure part width in pixels. Using any basic image viewer:
- Open the image and zoom to the part line
- Count the pixels across the visible scalp gap at a defined point (for example, 3 cm back from the frontal hairline)
- Record this number
- Compare across monthly sessions
This method does not give you an absolute measurement in millimeters, but the relative change in pixel count is a reliable trend indicator.
What Changes to Watch For
Gradual widening. A part that widens slowly over 6 to 12 months indicates chronic density loss, consistent with androgenetic alopecia. This is the classic pattern in female hair loss and diffuse male thinning.
Sudden widening. A part that widens noticeably within 1 to 3 months may indicate telogen effluvium (triggered by stress, illness, nutritional deficiency, or hormonal change) rather than androgenetic alopecia. Telogen effluvium is usually temporary and self-resolving once the trigger is addressed.
Asymmetric widening. If the part appears wider on one side than the other, this may reflect asymmetric thinning or a slight change in how you are creating the part. Verify your parting technique is consistent before attributing asymmetry to differential hair loss.
Density changes adjacent to the part. Look not just at the width of the gap but at the density of hair on either side. Thinning within 1 to 2 cm of the part, even if the gap width has not changed, indicates early-stage density loss that will eventually manifest as widening.
Combining Part Line With Full Tracking
Part line photos are most valuable when combined with other tracking angles. The part reveals central scalp density, while temple photos, crown photos, and top-of-head photos cover the remaining zones.
For the complete multi-angle tracking protocol, see our guide on consistent hair loss progress photos.
Measure Your Part Today
Your part line is the easiest zone to photograph and one of the most sensitive indicators of central scalp density. A single photo, taken consistently each month, builds a trend line that can detect changes well before they become visible in normal styling.
Upload your part line photos at myhairline.ai/analyze for AI-powered width analysis, density estimation, and month-over-month trend tracking.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Part line widening can result from multiple causes including androgenetic alopecia, telogen effluvium, and nutritional deficiencies. Consult a board-certified dermatologist for diagnosis and personalized treatment recommendations.