The Norwood-Hamilton scale is used by 95% of hair restoration surgeons for surgical planning and treatment decisions. It classifies male pattern baldness into 7 primary stages based on visual pattern recognition. But visual staging has a blind spot: it cannot detect the gradual density changes happening within each stage. AI density mapping fills this gap by adding quantitative measurements to the qualitative Norwood framework.
This guide explains each Norwood stage, what AI density data adds to each one, and how to use both systems together for the most complete hair loss tracking protocol available.
The 7 Norwood Stages Explained
Norwood 1: No Significant Hair Loss
Norwood 1 is the baseline. The hairline sits at its natural juvenile position with no recession at the temples and no thinning at the crown. No grafts are needed.
AI density value: Setting a Norwood 1 scan creates your personal density baseline. Caucasian hair at this stage averages 170 to 230 FU/cm2, Asian hair 140 to 200 FU/cm2, and African hair 120 to 180 FU/cm2. These numbers become your reference for all future measurements.
Norwood 2: Slight Temple Recession
Norwood 2 shows the first visible recession at the temples, creating a slight M-shaped hairline. The recession is typically symmetrical and mild. If transplanted, 800 to 1,500 grafts would be needed.
AI density value: Density measurement detects early temple miniaturization before visible recession is obvious. A drop of 10-15% in the temporal zones compared to baseline suggests early Norwood 2 even if the hairline still looks intact to the naked eye.
Norwood 3: Deep Temple Recession
Norwood 3 features deep recession at both temples, forming a pronounced M-shape. The frontal hairline has receded noticeably. Graft requirements: 1,500 to 2,200.
AI density value: At Norwood 3, AI density data distinguishes between 3 and 3A (uniform frontal recession without temple dominance). It also measures whether the frontal midline is thinning, which predicts the path toward Norwood 4.
Norwood 3 Vertex (3V): Temple Recession Plus Crown Thinning
Norwood 3V combines the temple recession of Norwood 3 with a distinct area of thinning at the crown (vertex). Graft requirements: 2,000 to 2,800.
AI density value: AI crown density measurement distinguishes 3 from 3V with precision. A crown density reading below the warning threshold for your ethnicity confirms vertex involvement. This classification changes treatment targeting significantly.
Norwood 4: Further Recession with Enlarged Vertex Area
Norwood 4 shows deeper frontal recession with an enlarged area of vertex thinning. A band of moderately dense hair separates the frontal and vertex zones. Graft requirements: 2,500 to 3,500.
AI density value: The critical measurement at Norwood 4 is the bridge zone density. If the bridge is intact (above 80% of baseline), you may actually be at Norwood 4A, which has a better transplant prognosis. AI data makes this distinction possible.
Norwood 5: Separation Between Front and Vertex Narrowing
Norwood 5 shows the band between the frontal and vertex zones becoming very narrow. The two bald areas are beginning to merge. Graft requirements: 3,000 to 4,500.
AI density value: Bridge density data at Norwood 5 determines how close you are to Norwood 6 (where the bridge disappears entirely). A bridge density reading below 50% of baseline suggests imminent progression.
Norwood 6: Bridge Lost, Horseshoe Pattern
Norwood 6 means the bridge has been lost. The frontal and vertex areas have merged into one large bald zone, leaving only the horseshoe band of hair on the sides and back. Graft requirements: 4,000 to 6,000.
AI density value: At Norwood 6, the focus shifts to donor area density. AI measurement of the occipital and temporal donor regions determines how many grafts can be safely extracted (at the 45% safe extraction limit) for transplantation.
Norwood 7: Most Extensive Hair Loss
Norwood 7 is the most advanced stage. Only a narrow horseshoe band remains, and it is typically narrower than at Norwood 6. Graft requirements: 5,500 to 7,500.
AI density value: Donor density measurement is essential at Norwood 7 because the donor supply is the limiting factor for all treatment options. Residual miniaturized hair mapping in the bald zone also helps surgeons plan channel placement for transplanted grafts.
Complete Norwood Staging and Graft Reference
| Stage | Description | Grafts Required | Cost Range (USA) | Cost Range (Turkey) |
|---|---|---|---|---|
| Norwood 1 | No loss | 0 | $0 | $0 |
| Norwood 2 | Slight temple recession | 800-1,500 | $3,200-$9,000 | $800-$3,000 |
| Norwood 3 | Deep temple recession | 1,500-2,200 | $6,000-$13,200 | $1,500-$4,400 |
| Norwood 3V | Temples + crown | 2,000-2,800 | $8,000-$16,800 | $2,000-$5,600 |
| Norwood 4 | Enlarged vertex area | 2,500-3,500 | $10,000-$21,000 | $2,500-$7,000 |
| Norwood 5 | Narrowing bridge | 3,000-4,500 | $12,000-$27,000 | $3,000-$9,000 |
| Norwood 6 | Bridge lost | 4,000-6,000 | $16,000-$36,000 | $4,000-$12,000 |
| Norwood 7 | Most extensive | 5,500-7,500 | $22,000-$45,000 | $5,500-$15,000 |
Why Visual Staging Alone Falls Short
The Norwood scale has been the standard since Dr. O'Tar Norwood revised Hamilton's original classification in 1975. It works well for broad categorization. However, it has three limitations that AI density data addresses.
Limitation 1: Wide Ranges Within Stages
Each Norwood stage covers a range of severity. A man at early Norwood 3 has a very different clinical picture from one at late Norwood 3 about to transition to Norwood 4. Visual staging cannot distinguish between these positions. AI density data shows exactly where within a stage you are.
Limitation 2: No Detection of Early Changes
A density drop of 15% in the temporal zone may be clinically significant but visually invisible. By the time recession is visible to the eye, the density has already decreased substantially. AI measurement catches density changes of 5-10% that are months ahead of visual detection.
Limitation 3: No Rate-of-Change Measurement
Looking at a single Norwood stage tells you where you are, not how fast you are moving. Two men at Norwood 3 could have arrived there over 5 years (slow progression) or 18 months (fast progression). Their treatment needs are very different. AI density scans over time calculate your personal progression rate.
How AI Density Data Integrates with Norwood Staging
The AI does not replace Norwood staging. It enhances it with three layers of additional data.
Layer 1: Intra-stage positioning. Your density per cm2 in each zone places you at a specific point within your Norwood stage. The system tracks your position within the stage over time, so you can see movement toward the next stage months before a visual change occurs.
Layer 2: Zone-specific granularity. The Norwood scale describes overall patterns. AI data breaks your scalp into 5 or more independent zones, each with its own density measurement. This catches asymmetric loss, variant patterns (2A, 3A, 4A, 5A), and zone-specific treatment responses that a single Norwood label cannot represent.
Layer 3: Progression rate calculation. With 3 or more scans over 6+ months, the system calculates your personal progression rate in density units per month. This rate, combined with your current stage, projects your future trajectory and informs treatment intensity decisions.
Setting Up Your Norwood + AI Tracking Protocol
Initial Scan
Upload photos of all five scalp zones to myhairline.ai/analyze:
- Frontal hairline (straight on, hair pulled back)
- Left temple (45-degree left profile)
- Right temple (45-degree right profile)
- Crown (top-down, looking straight down)
- Donor area (back of head)
The AI returns your Norwood stage, density per cm2 for each zone, and your position within that stage.
Ongoing Monitoring
| Your Stage | Scan Frequency | What to Watch |
|---|---|---|
| Norwood 1 | Every 3-6 months | Any density drop from baseline |
| Norwood 2-3 | Monthly | Temple zone density, frontal midline position |
| Norwood 3V-4 | Monthly | Crown density, bridge zone stability |
| Norwood 5-6 | Monthly | Donor density, bridge/crown progression |
| Norwood 7 | Quarterly (stable stage) | Donor density preservation only |
Treatment Response Tracking
If you are on treatment, your scans measure response in real density units rather than subjective visual assessment.
| Treatment | What AI Data Shows | Expected Timeline |
|---|---|---|
| Finasteride 1mg | Density stabilization or increase | 3-6 months to detect |
| Minoxidil 5% | Zone-specific density change | 4-6 months to detect |
| PRP therapy | Density increase in treated zones | After 3-4 sessions |
| Post-transplant | Graft survival and new growth density | 3-12 months |
Finasteride halts further loss in 80-90% of men and produces regrowth in 65%. Side effects affect 2-4% of users. Minoxidil produces moderate regrowth in 40-60% of users. PRP shows 30-40% density increase at $500 to $2,000 per session.
The Combined Tracking Advantage
Using Norwood staging and AI density data together gives you the complete picture. The Norwood stage provides a universally understood label that any dermatologist or surgeon recognizes. The AI density data provides the precision measurements that drive informed treatment decisions and detect changes before they become visible.
Every consultation is stronger when you walk in with both your Norwood stage and your zone-specific density data over time.
Get Your AI-Enhanced Norwood Assessment
Upload your scalp photos at myhairline.ai/analyze for your Norwood stage classification plus zone-by-zone density data. Your first scan takes under 5 minutes and creates the foundation for precision hair loss tracking.
This content is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any hair loss treatment.
FAQ
What are the 7 Norwood scale stages?
Norwood 1 is no significant loss. Norwood 2 is slight temple recession. Norwood 3 is deep temple recession forming an M-shape. Norwood 3V adds vertex thinning. Norwood 4 has further recession with an enlarged vertex area. Norwood 5 shows narrowing separation between front and vertex. Norwood 6 loses the bridge between areas. Norwood 7 is the most extensive loss with only a narrow band remaining.
How does AI density data improve on visual Norwood staging?
Visual Norwood staging places you in one of 7 broad categories. AI density data measures your exact follicular unit count per cm2 in each scalp zone, detecting 5-10% density changes that are invisible to the eye. This catches progression months before a visual stage change would be noticed.
Can myhairline.ai automatically classify my Norwood stage?
Yes. Upload photos of your hairline, temples, and crown. The AI measures density in each zone and maps those measurements to the corresponding Norwood stage. It also provides the raw density data so you can track changes within a stage, not just between stages.