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 its 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).
[edit] Related articles on Designing Buildings
- Drawing board.
- Manual drafting techniques.
- Notation and units on drawings and documents.
- Paper sizes.
- Rotring.
- Scale drawing.
- Shop drawings.
- Standard hatching styles for drawings.
- Symbols on architectural drawings.
- T-square.
- Technical drawing pen sizes.
- Types of drawing.
- Types of paper.
- Technical drawing.
- Working drawings.
Featured articles
Check out some of the best features and news from Designing Buildings as well as key stories from around the web.
Cut electricity bills to power growth
Coalition sends joint letter to the Chancellor.
Gasholders: a history in pictures. Book review.
Recognition, influence and growth
SocEnv identifies three strategic pillars in new strategy to 2045.
Discover the future of roofing, cladding and insulation.
New guidance for professional practice, cultural change and regulation in social housing.
The heritage of nuclear and conventional power stations.
New measures to stop people being ripped off
Government to protect families from cowboy builders and aggressive bailiffs.
New Futurebuild showcase brings an innovation-first approach.
National Planning Policy Framework
Understanding the 2026 changes.
ECA's public affairs priorities
Member consultation opens to shape priorities for 2027 to 2030.
Dutyholder responsibilities from 1 July 2026.
Where performance meets practice
The Building Envelope Stage at UKCW Birmingham.