Lead Hardness Scale vs. Mechanical Pencil Leads
Comparing 2 standards across 13 specifications. 13 key differences identified.
The Graphite Hardness Grading Scale (standardized under ISO 15184 and ASTM D3363) classifies pencil graphite from 9H (hardest, lightest grey, highest clay content) through HB (medium equilibrium) to 9B (softest, darkest black, highest graphite content). HB is the universal writing standard and the exact equivalent to the North American No. 2 pencil.
Mechanical Pencil Lead Sizes (standardized under ISO 9177-2) define polymer-bonded graphite refill diameters: 0.2 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, and 2.0 mm leadholders, with a standard length of 60.0 mm. Sized for specific drafting and handwriting pressures, 0.5 mm is the universal drafting standard and 0.7 mm is the heavy-pressure writing standard.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Hard Grade Range (9H to 2H)
|
9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H — high clay/polymer binder ratio, crisp hairline precision, zero smudging | — |
|
Medium Equilibrium Range (H, F, HB, B)
|
H (Hard), F (Fine point retention), HB (Hard Black — standard writing balance), B (Black) | — |
|
Soft Grade Range (2B to 9B)
|
2B, 3B, 4B, 5B, 6B, 7B, 8B, 9B — high graphite content, deep velvety blacks, artistic shading | — |
|
US No. 2 Pencil Equivalent
|
HB grade (mandatory for optical Scantron standardized bubble test optical scanners) | — |
|
US Numbering System Cross-Check
|
#1 = B | #2 = HB | #2.5 = F | #3 = H | #4 = 2H | — |
|
Origin
|
Developed by Joseph Hardtmuth of Koh-i-Noor in Vienna (1790s), who introduced the H/B alphanumeric system | — |
|
0.2 mm Lead (Pentel Orenz)
|
— | 0.20 mm — ultra-micro drafting and mathematical annotation (requires sliding guide pipe) |
|
0.3 mm Lead (Drafting)
|
— | 0.35 mm actual diameter — technical engineering drafting, complex kanji, fine stippling |
|
0.5 mm Lead (Universal)
|
— | 0.50 mm actual diameter — the global standard for students, drafting, and office writing |
|
0.7 mm Lead (Heavy Pressure)
|
— | 0.70 mm actual diameter — robust everyday writing, resists snapping under heavy hand pressure |
|
0.9 mm Lead / 1.3 mm Lead
|
— | 0.90 mm to 1.30 mm — woodworking carpentry, standardized test bubble filling, primary school |
|
2.0 mm Leadholder (Clutch Pencil)
|
— | 2.00 mm diameter × 130 mm length — architectural sketching, requires rotary lead pointer sharpener |
|
Standard Refill Length
|
— | 60.0 ± 1.0 mm (for 0.2 mm to 0.9 mm polymer high-polymer leads) |