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Pen Sizes and Line Types (Metric)

Last updated July 29, 2026

By Steve

Nine technical drafting pens with their ISO colour codes and nib widths in mm: 0.13 magenta, 0.18 red, 0.25 white, 0.35 yellow, 0.50 brown, 0.70 blue, 1.00 orange, 1.40 green and 2.00 grey
Colors on the old drafting pens
The ISO defines a set of standard metric line widths for drafting.
Like the ISO A and B series sheet sizes, the pen sizes increase by a factor of 2. This allows additions and corrections to be made on the enlargements or reductions of drawings.
Each width is assigned a color code. The color code corresponds to that for the matching lettering stencil.
Line widths and color codes are standardized across all manufacturers.
 
Letter Type of Line Line Thickness (mm) Application
    A0 A1 A2
A3
A4		  
A Continuous – thick

Type A line sample: continuous thick
 
 0.7 0.5 0.35
  • Visible outlines
B Continuous – thin

Type B line sample: continuous thin
 
 0.35 0.25 0.18
  • Fictitious outlines
  • Imaginary intersection of surfaces
  • Dimension lines, projection lines, intersection lines and leaders
  • Hatching
  • Outlines of revolved sections
  • Adjacent parts and tooling
  • Fold and tangent bend lines
  • Short centerlines
C Continuous – thin, freehand or ruled with zig-zag

Type C line sample: continuous thin, drawn freehand with an irregular wavering path and a zig-zag break

 
 0.35 0.25 0.18
  • Indication of repeated detail
  • Break lines (other than on an axis)
D Dashed – medium

Type D line sample: dashed medium, evenly spaced dashes

 
 0.50 0.35 0.25
  • Hidden outlines
E Chain – thin

Type E line sample: chain thin, long dashes separated by short ticks

 
 0.35 0.25 0.18
  • Centerlines
  • Pitch lines
  • Alternative position of moving part
  • Path lines for indicating movement
  • Features in front of a cutting plane
  • Developed views
  • Material to be removed
F Chain – thick at ends and at change of direction, thin elsewhere

Type F line sample: chain, thick at each end and at changes of direction, thin along the middle
 
 0.7
0.35		 0.5
0.25		 0.35
0.18
  • Cutting planes
G Chain – thick

Type G line sample: chain thick
 
 0.7 0.5 0.35
  • Indication of surfaces to meet special requirements