PCT Patent Drawing Requirements: A Practical Guide

PCT patent drawing requirements are the formal rules in WIPO's PCT Regulations (Rules 11.13 and 11.14) that govern how figures must be prepared for international applications. You must use A4 paper, 2.5 cm minimum margins, black durable lines, numbered figures, and reference numerals that match the description — or risk an invitation to correct defects.

What are the basic PCT patent drawing requirements?

For any international application filed under the Patent Cooperation Treaty, drawings must be executed in durable, black, sufficiently dense and dark, uniformly thick and well-defined lines and strokes without colorings. The paper must be A4 (29.7 cm × 21 cm), flexible, strong, white, smooth, non-shiny, and durable. Each sheet must have a minimum margin of 2.5 cm on the top, 2.5 cm on the left, 1.5 cm on the right, and 1 cm on the bottom. These are the foundational WIPO drawing standards that every applicant should treat as non-negotiable.

Drawings must be arranged upright and, where possible, with the longer side vertical. They must not contain text matter, except a single word or words such as "water," "steam," "open," "closed," "section A-A," and—in electric circuits and block schematic diagrams—short catchwords indispensable for understanding. Numbers, letters, and reference lines must be simple and clear, and brackets, circles, or inverted commas around numbers and letters are not permitted.

How should PCT figures be numbered and labeled?

All sheets of drawings contained in an international application must be numbered in consecutive Arabic numerals, independently of the numbering of the description pages and claims. The figures themselves must also be numbered consecutively in Arabic numerals, independently of the sheet numbering. The standard PCT figure rules require that reference signs not mentioned in the description and claims must not appear in the drawings, and vice versa. The same features, when denoted by reference signs, must be denoted by the same signs throughout the international application.

If the application contains a large number of figures, they may be placed on several sheets. Each figure must be clearly separated from the others by a blank space of at least 0.5 cm. Where figures on two or more sheets form in effect a single complete figure, the figures on the several sheets must be so arranged that the complete figure can be assembled without concealing any part of any of the figures.

What are the PCT rules for shading, scale, and line quality?

Shading is allowed where it helps to show the shape of an object, but it must be executed with well-defined lines and must not be used to indicate color. The scale of the drawings and the distinctness of their graphical execution must be such that a photographic reproduction with a linear reduction in size to two-thirds would enable all details to be distinguished without difficulty. If a scale is drawn on a figure, it must be represented graphically rather than as a numerical ratio.

For international patent drawings, cross-sections must be indicated by hatching that does not impede the clear reading of reference signs and leading lines. The hatching lines should be oblique and evenly spaced, and different parts of the same figure should be hatched differently where necessary to distinguish materials or regions. No drawing may contain a frame around it, and no lead lines may cross each other where avoidable.

Step-by-step workflow for preparing compliant PCT drawings

Follow this numbered workflow to reduce the chance of a formal defect notice from the receiving Office or the International Bureau:

1. Confirm the drawing sheet format. Use A4 size only. If you inherit drawings on US Letter, convert and re-check margins before filing.
2. Set margins in your drafting tool. Top 2.5 cm, left 2.5 cm, right 1.5 cm, bottom 1 cm. Do not draw inside these zones.
3. Draft figures in black vector lines. Avoid gray fills, color gradients, and photographs. Export as high-resolution line art, not raster scans.
4. Number every figure and every sheet. Figures: Fig. 1, Fig. 2, etc. Sheets: 1/4, 2/4, etc. Keep the two numbering systems independent.
5. Insert reference numerals consistently. Use the same numeral for the same part in every figure and in the description and claims.
6. Add only permitted text. Words like "section A-A" or "open" are allowed; explanatory paragraphs are not.
7. Check line weight and shading. Lines must survive two-thirds reduction. Hatching must not obscure numerals.
8. Review against Rule 11.13 checklist. Verify margins, paper quality, line darkness, absence of color, and no frames.
9. Export and test-print. Print at 66% scale on A4 and confirm every numeral remains legible.
10. File and retain the original. Keep the native file in case the International Searching Authority requests replacement sheets.

Concrete example: a mechanical device figure set

Imagine you are filing a PCT application for a collapsible bicycle pedal. Your drawing set includes four figures: Fig. 1 is a perspective view of the pedal in use, Fig. 2 is an exploded view, Fig. 3 is a cross-section along line A-A, and Fig. 4 is a detail view of the locking mechanism.

Under PCT figure rules, you would number the pedal body as 10, the spindle as 12, the locking collar as 14, and the spring as 16 in every figure. In Fig. 3, the cross-section hatching would run at 45 degrees on the pedal body and at a different angle on the spindle, without touching any reference numeral. The only text on the sheet would be "Fig. 3" and, if needed, "Section A-A." The sheet itself would be marked "1/2" at the top if the set spans two sheets, with all four figures arranged upright and separated by at least 0.5 cm of blank space.

This example illustrates how WIPO drawing standards translate into everyday drafting decisions: consistent numerals, restrained text, purposeful hatching, and a layout that survives reduction.

Common mistakes that trigger PCT drawing objections

• Using US Letter instead of A4. The PCT requires A4; Letter sheets create margin and scale problems and invite a formal defect notice.
• Placing reference numerals that are not in the description. Rule 11.13 requires strict correspondence. A numeral that appears only in a drawing is a defect.
• Including photographs or grayscale renders. Photographs are only permitted in exceptional cases where they are the only practicable medium, and they still must be black-and-white and direct-positive.
• Adding frames or borders around figures. Frames are expressly prohibited and are a frequent reason for replacement sheet requests.
• Using color or thin gray lines. Color is not accepted in international patent drawings, and lines that cannot survive two-thirds reduction will be rejected.
• Writing explanatory text inside the drawing. More than a single word or indispensable catchword is a formal defect.
• Letting lead lines cross. Crossing lead lines make figures harder to read and can trigger a clarity objection.
• Numbering sheets and figures with the same sequence. The two numbering systems must be independent and clearly distinct.

If you are preparing drawings in a drafting workspace, tools like PatentDraw can help you set A4 templates, maintain numeral consistency, and export black-and-white vector files that align with PCT figure rules. However, AI-generated or template-based output is a working draft and requires human technical and professional review before filing.

Frequently asked questions

What paper size is required for PCT patent drawings?

PCT patent drawings must be on A4 paper (29.7 cm × 21 cm). The paper must be white, smooth, non-shiny, flexible, and durable, with margins of at least 2.5 cm top and left, 1.5 cm right, and 1 cm bottom.

Can PCT drawings be in color?

No. PCT drawings must be executed in black, durable, sufficiently dense and dark lines. Color drawings are not accepted in international applications, and photographs are only permitted in exceptional cases where they are the only practicable medium for showing the invention.

Do PCT drawings need reference numerals that match the description?

Yes. Reference signs in the drawings must correspond exactly to those in the description and claims. A numeral that appears in a drawing but not in the text, or in the text but not in a drawing, is a formal defect under Rule 11.13.