Hamilton-Norwood Scale Complete Guide: Tracking Every Stage
The Hamilton-Norwood scale was developed in 1951 and remains the primary classification tool used by hair restoration surgeons worldwide. This guide covers every stage in detail, including the graft requirements, treatment options, and how AI density tracking adds quantitative depth that visual staging cannot provide.
The History Behind the Scale
Dr. James Hamilton published the original male pattern baldness classification in 1951 after studying the role of androgens in hair loss. His system identified the basic patterns of progression in androgenetic alopecia.
In 1975, Dr. O'Tar Norwood revised Hamilton's work, adding intermediate stages and the vertex variant that clinicians still reference today. The combined system became the Hamilton-Norwood scale, though most practitioners simply call it the Norwood scale.
The scale has remained fundamentally unchanged for over 50 years. It is simple, visual, and universally understood. But it has a significant limitation: it describes the pattern of loss without measuring the density within that pattern.
Why Visual Staging Has a Blind Spot
The Norwood scale tells you where hair is receding. It does not tell you how dense the remaining hair is within each zone. Two men can both be classified as Norwood 3, yet one may have 180 follicular units per square centimeter in his mid-scalp zone while the other has 120.
That 33% density difference is invisible to visual staging but critical for treatment planning.
AI density tracking fills this gap by measuring follicular unit density across multiple zones, creating a continuous data stream that reveals intra-stage progression before the pattern visually advances to the next Norwood number.
Stage-by-Stage Breakdown
Norwood 1: No Significant Hair Loss
Pattern: Full head of hair with a mature hairline. Minimal to no recession at the temples.
Density range: 170 to 230 follicular units per cm2 (varies by ethnicity)
| Ethnicity | Typical Density (FU/cm2) |
|---|---|
| Caucasian | 170 to 230 |
| African | 120 to 180 |
| Asian | 140 to 200 |
| Hispanic | 145 to 195 |
| Middle Eastern | 150 to 210 |
Treatment: No intervention needed. This is the ideal stage for establishing a tracking baseline if you have a family history of hair loss.
Grafts needed: 0
Tracking value: Establishing a baseline density at Norwood 1 gives you the reference point against which all future measurements are compared. Men with strong family history should start tracking here.
Norwood 2: Slight Temple Recession
Pattern: Mild recession at the temples creating a slight M-shape. This is where many men first notice changes.
Grafts if transplanting: 800 to 1,500
Treatment options:
- Finasteride (80 to 90% halt further loss, 65% experience regrowth)
- Minoxidil (40 to 60% experience moderate regrowth)
- Monitoring and lifestyle optimization
| Treatment Cost by Location | Low Estimate | High Estimate |
|---|---|---|
| USA (800 to 1,500 grafts) | $3,200 | $9,000 |
| UK (800 to 1,500 grafts) | $2,400 | $7,500 |
| Turkey (800 to 1,500 grafts) | $800 | $3,000 |
| India (800 to 1,500 grafts) | $400 | $2,250 |
Tracking value: AI tracking detects the 10 to 15% density decline at the temples that precedes visible Norwood 2 recession. Early detection at this stage enables medical intervention before the pattern becomes cosmetically noticeable.
Norwood 3: Deep Temple Recession
Pattern: Distinct M-shaped recession at both temples. The hairline has moved back significantly from its original position.
Grafts if transplanting: 1,500 to 2,200
Treatment options:
- Finasteride (strongly recommended at this stage)
- Minoxidil (topical, for the frontal zone)
- Hair transplant (FUE recovery: 7 to 10 days, 90 to 95% graft survival)
- Combination therapy
Tracking value: At Norwood 3, tracking the rate of progression is critical. A man losing 8 to 10% density per year needs a different strategy than one losing 2 to 3% per year. AI density measurements over 6 to 12 months reveal your personal progression rate, which directly informs transplant timing.
Norwood 3 Vertex: Temple Recession Plus Crown Thinning
Pattern: Same temple recession as Norwood 3, plus noticeable thinning at the crown (vertex). This variant is particularly important because it signals activity in two separate zones.
Grafts if transplanting: 2,000 to 2,800
Treatment options:
- Finasteride (essential for dual-zone loss)
- Minoxidil (particularly effective on the vertex)
- PRP ($500 to $2,000 per session, 30 to 40% density increase in clinical studies)
- Combined medical therapy before considering transplant
Tracking value: The 3V variant requires zone-specific tracking. AI density measurements on both the frontal and vertex zones independently reveal which area is progressing faster, helping you and your surgeon prioritize treatment.
Norwood 4: Further Recession with Enlarged Vertex
Pattern: Deeper frontal recession with a larger bald spot at the crown. A bridge of moderately dense hair still separates the two areas.
Grafts if transplanting: 2,500 to 3,500
Treatment options:
- Maximum medical therapy (finasteride + minoxidil + PRP)
- Hair transplant planning (assess donor density)
- The bridge zone density determines how urgently transplant should be considered
Tracking value: Norwood 4 is the stage where the bridge zone between frontal and vertex loss becomes the critical measurement area. AI tracking of bridge zone density predicts when Norwood 4 will advance to Norwood 5, giving you a planning window for surgical intervention.
Norwood 5: Bridge Narrowing
Pattern: The bridge of hair between the frontal and vertex areas has thinned significantly. The two zones of loss are beginning to merge.
Grafts if transplanting: 3,000 to 4,500
Donor zone considerations become critical at this stage. The safe extraction limit is 45% of available donor follicles. At Norwood 5, you must calculate whether your donor supply can cover the recipient area adequately.
| Donor Zone Density | Available Grafts (45% safe limit) | Sufficient for N5? |
|---|---|---|
| 80 FU/cm2 (low) | ~2,800 | Borderline |
| 100 FU/cm2 (average) | ~3,500 | Yes |
| 120 FU/cm2 (high) | ~4,200 | Yes, with margin |
Tracking value: At Norwood 5, tracking both the recipient area loss and the donor zone density is essential. AI tracking of the donor zone ensures you are not depleting your supply beyond what is safe for potential future procedures.
Norwood 6: Horseshoe Pattern
Pattern: The bridge between frontal and vertex areas is gone. Hair loss forms a continuous bald area across the top of the scalp, with hair remaining in a horseshoe pattern around the sides and back.
Grafts if transplanting: 4,000 to 6,000
Treatment reality: At Norwood 6, full coverage restoration is challenging. Most surgeons focus on creating density in the most cosmetically impactful areas (frontal framing) rather than attempting full coverage.
| Priority Zone | Graft Allocation | Cosmetic Impact |
|---|---|---|
| Frontal hairline | 1,500 to 2,000 grafts | Highest (frames the face) |
| Mid-scalp | 1,000 to 1,500 grafts | Moderate |
| Crown | 1,000 to 2,000 grafts | Lower priority |
Tracking value: Post-transplant tracking at Norwood 6 is where AI density measurements are most valuable. Monitoring graft survival across each zone and detecting any continued native hair loss helps plan maintenance treatments.
Norwood 7: Most Extensive Loss
Pattern: Only a narrow band of hair remains around the sides and back of the head. This represents the maximum extent of androgenetic alopecia.
Grafts if transplanting: 5,500 to 7,500
Treatment reality: Complete restoration is not possible at Norwood 7 for most patients. Donor supply limitations mean surgeons must be highly strategic about graft placement. Some patients opt for scalp micropigmentation (SMP) combined with limited transplant work.
Tracking value: For Norwood 7 patients, AI tracking serves two purposes. First, it monitors the density of the remaining donor zone to determine transplant candidacy. Second, for patients who have had transplant work, it tracks graft survival and identifies any continued miniaturization in the donor band.
The Tracking Advantage: Continuous vs. Snapshot Assessment
Traditional Norwood staging is a snapshot. You visit a clinic, a surgeon looks at your head, and assigns a number. That number does not change until your next visit, even if your density is declining between appointments.
AI density tracking converts this snapshot into a continuous data stream:
| Assessment Method | Data Points Per Year | Intra-Stage Detection | Progression Rate |
|---|---|---|---|
| Annual clinic visit | 1 | No | No |
| Quarterly clinic visit | 4 | Unlikely | Rough estimate |
| Monthly AI tracking | 12 | Yes | Precise trend |
| Bi-weekly AI tracking | 26 | Yes | High-resolution trend |
The practical result: tracking catches a density decline of 10 to 15% that occurs within a Norwood stage, months before it becomes visible as a pattern change to the next stage.
How to Use the Scale with AI Tracking
The Hamilton-Norwood scale and AI density tracking are complementary, not competing, tools. Here is how to use them together:
- Get your Norwood classification from a dermatologist or hair restoration surgeon.
- Establish your baseline density across all zones using myhairline.ai.
- Track monthly to detect intra-stage density changes.
- Use the Norwood stage for communication with clinicians (it is the universal language of hair loss).
- Use the density data for decision-making (treatment changes, transplant timing, response assessment).
The Norwood number tells you where you are. The density data tells you how fast you are moving and whether your treatment is working.
Start Tracking Your Stage
Whether you are Norwood 1 building a baseline or Norwood 6 monitoring post-transplant results, objective density data improves every decision you make.
Get your free AI density analysis at myhairline.ai/analyze and pair your Norwood classification with the quantitative data it needs.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. The Hamilton-Norwood scale is a clinical classification tool that should be assessed by a qualified hair restoration specialist. Graft counts, treatment efficacy, and density ranges are approximate and vary by individual. Always consult a board-certified dermatologist or hair restoration surgeon for personalized guidance.