Technical drawing pen sizes

Technical drawing pens follow the same size-ratio principle as A series paper sizes, that is, an aspect ration of 1:√2, with the progression proceeding by folding the preceding size in two. When an A size piece of paper is folded in two it retains it's proportions.

The standard sizes for technical drawings pens also differ by a factor √2, ie. 2.00 mm, 1.40 mm, 1.00 mm, 0.70 mm, 0.50 mm, 0.35 mm, 0.25 mm, 0.18 mm, 0.13 mm.

This means for example that after drawing with a 0.35 mm pen on A3 paper and reducing it to A4, you can continue with the 0.25 mm pen. (ISO 9175-1).

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[edit] Related articles on Designing Buildings Wiki

• Manual drafting techniques.
• Notation and units on drawings and documents.
• Paper sizes.
• Shop drawings.
• Standard hatching styles for drawings.
• Symbols on architectural drawings.
• Types of drawing.
• Technical drawing.
• Working drawings.