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EPO Drawing Requirements: 7 Critical Rules for 2026

April 24, 2026 Aruna 15 min read
EPO drawing requirements — intellectual property law and protection

The European Patent Office (EPO) imposes rigorous formal standards on all drawings submitted with European patent applications. EPO drawing requirements are governed primarily by Rule 46 of the European Patent Convention (EPC) and supplementary EPO guidelines for examination. Applicants who overlook EPO drawing requirements often receive Article 90(3) EPC formality examination deficiencies that add months to the prosecution timeline and require costly corrected drawings to be prepared and filed.

This guide covers the essential EPO drawing requirements practitioners need to understand for successful European prosecution, with comparisons to USPTO standards where differences are significant. Whether you are preparing an original European application or converting a PCT application into the European regional phase, compliance with EPO drawing requirements from the outset is the most efficient path to grant.

What Are EPO Drawing Requirements?

EPO drawing requirements are the formal technical standards that all drawings submitted to the European Patent Office must satisfy. These standards are set out in Rule 46 EPC, supplemented by the EPO Guidelines for Examination and the Rules Relating to Fees. EPO drawing requirements govern paper size, margins, line quality, reference signs, figure numbering, and text within drawings. Unlike the USPTO, the EPO formality examination typically occurs before substantive examination, meaning that EPO drawing requirements must be satisfied early in the prosecution timeline to avoid delays entering the substantive phase.

EPO drawing requirements also interact with claim drafting in ways that US practitioners may find unfamiliar. Under European practice, claims must be supported by the drawings, and the EPO specifically requires that all reference signs in the claims correspond to reference signs used in the drawings. This connection between EPO drawing requirements and claim structure makes it essential to finalize drawings before or alongside the drafting of claims.

Paper Size Under EPO Drawing Requirements

EPO drawing requirements mandate A4 paper (21.0 cm × 29.7 cm) as the standard paper size for all drawing sheets. This is a key distinction from USPTO practice, which accepts both letter-size and A4 paper. When preparing drawings for dual filing at the USPTO and EPO, practitioners should use A4 paper to satisfy both offices without modification. EPO drawing requirements do not accept letter-size paper for original European applications, and applicants who inadvertently submit letter-size sheets will receive a formality deficiency requiring corrected drawings.

Margin Requirements Under Rule 46 EPC

Margins are precisely specified in EPO drawing requirements. Under Rule 46(2)(c) EPC, the minimum margins are: top 2.5 cm, left 2.5 cm, right 1.5 cm, and bottom 1.0 cm. The left margin specification in EPO drawing requirements is particularly important because the EPO uses the left margin area for official stamps and notations during formality examination. Any drawing element that encroaches on the left 2.5 cm margin will generate a formal deficiency. The usable drawing surface on A4 paper compliant with EPO drawing requirements is therefore approximately 17.5 cm × 26.2 cm.

Line Quality and Technical Standards

EPO drawing requirements specify that lines must be durable, uniform, clean, and sufficiently dense and dark to permit good electronic reproduction. Rule 46(2)(e) EPC states that elements of the drawings must be executed in durable, black, uniformly thick and well-defined strokes and lines. EPO drawing requirements prohibit half-tones, gray shading, gradients, and photographs except in limited circumstances where color is essential to understanding the invention and special authorization has been granted. All line work must be capable of being reproduced clearly at a reduction of up to one-third without loss of detail—a practical standard that drives the minimum line weight typically used in EPO-compliant drawings.

Reference Signs and Figure Numbering

EPO drawing requirements impose specific rules on reference signs that differ subtly from USPTO practice. Under Rule 46(3) EPC, the drawings must not contain text matter, except for single words—such as “water,” “steam,” or labels like “open” and “closed”—that are indispensable for understanding the drawings. Arabic numerals must be used for reference signs unless the application was filed with letters, in which case both may be used. EPO drawing requirements require that all reference signs in the drawings correspond to the reference signs used in the description and claims, and that no reference sign be used in the drawings that is not mentioned in the description.

Figure numbering under EPO drawing requirements must follow a consecutive sequence using Arabic numerals. Where multiple figures appear on a single drawing sheet, each figure must be clearly separated from the others and numbered separately as Fig. 1, Fig. 2, and so on. EPO drawing requirements also specify that figures depicting the same subject matter from different angles should use the same reference signs for the same components, maintaining consistency across all views throughout the application.

EPO Drawing Requirements vs USPTO: Key Differences

While EPO and USPTO drawing requirements share the same fundamental goals—durable, legible, reproducible drawings—practitioners who work in both jurisdictions must be aware of the practical differences. The most important distinction is paper size: the EPO requires A4 exclusively while the USPTO accepts both A4 and letter size. EPO drawing requirements impose a stricter left margin of 2.5 cm compared to the USPTO’s requirement, which is helpful when drawings prepared for EPO filing are later used in US national phase applications.

Drawing standards are also stricter about text within drawings. While the USPTO permits more descriptive labels and annotations within drawing figures, the EPO restricts text within drawings to single indispensable words. This restriction under Formal drawing rules means that US practitioners must often prepare separate drawing sets for EPO and USPTO filings when the US drawings contain more extensive textual annotations. Working with a patent attorney experienced in both systems from the outset avoids the cost of preparing two separate drawing sets. See our full comparison in our guide on patent drawing requirements for USPTO and EPO.

Rule 46 EPC Was Deleted: What Governs the Form of Drawings Now

If you have been working from a checklist that cites Rule 46 EPC, that checklist is out of date. Rule 46 EPC no longer exists. The EPO’s own published legal text now renders the provision as “Rule 46 – (deleted)”.

Rule 46 EPC and Rule 49(3) to (12) EPC were deleted with effect from 1 February 2023, by a decision of the Administrative Council taken at its 172nd session on 13 October 2022 as part of the EPO’s digital-transformation package. Rules 49(2), 50, 57(i) and 82(2) EPC were adapted at the same time so the remaining text reads consistently.

What replaced them is a different kind of instrument. The form requirements for drawings moved into a Decision of the President of the EPO, published in the Official Journal. That is a deliberate structural choice: the office can now revise presentation rules by presidential decision and a notice in the OJ, without going through the Administrative Council to amend the Implementing Regulations. The practical consequence for you is that the governing text can change faster than the Convention ever did, so a drawing standard checked once and filed away will drift.

Three things follow for day-to-day prosecution. First, the substantive expectations did not evaporate — sheets still have to be reproducible, legible and consistent, and Rule 49(2) EPC continues to require application documents to be in a form admitting of both electronic and direct reproduction. Second, the operative detail now sits in the presidential decision and in Part A, Chapter IX of the EPO Guidelines for Examination rather than in a numbered Rule you can cite from memory. Third, anything in your own precedents, templates or client-facing material that describes Rule 46 EPC as live law should be corrected, because it is the kind of error opposing counsel notices.

One caution on research. Several widely used unofficial EPC resources still display Rule 46 as an active provision, and at least one popular consolidated-text site has not updated it. Check the form of the drawings against the EPO’s own legal texts and Official Journal notices at epo.org, not against a mirror.

Colour and Greyscale Figures at the EPO Since 1 October 2025

The deletion of Rule 46 was procedural groundwork. The substantive change arrived later, and it reversed one of the oldest constraints in European patent drafting.

Since 1 October 2025 the EPO accepts drawings filed electronically in colour or greyscale, under a Decision of the President published at OJ EPO 2025, A49 and explained in the accompanying Notice at OJ EPO 2025, A57. The figures must be contrast-rich and clear at 300 dpi — the office is protecting reproducibility, not inviting decorative shading.

Two limits matter. The concession covers drawings only: the description, claims and abstract remain black and white. And it applies to electronic filing, which is how the great majority of European applications arrive in any event.

This genuinely changes drafting options for subject matter that resisted line work — histology, fluorescence imaging, heat maps, multi-layer semiconductor stacks, anything where colour was carrying information that hatching reproduced badly. Our detailed treatment of EPO colour patent drawings covers how far the concession reaches.

The trap is assuming the rest of the system moved with the EPO. It did not. The PCT was not amended: PCT Rule 11.13(a) still requires drawings to be executed in durable, black, sufficiently dense and dark, uniformly thick and well-defined lines and strokes without colourings. For a Euro-PCT case the EPO will work from colour only where colour drawings are actually on PATENTSCOPE and the international publication says so, which depends on what the receiving Office and the International Bureau did with them at the international stage.

So a single colour figure set can be valid at the EPO on direct European filing, degraded on the international route, and inadmissible on several national routes at once. If a family is going to more than one office, decide early whether colour is load-bearing or merely convenient, and keep a compliant monochrome version of every sheet. Our side-by-side of the PCT drawing requirements is the cross-check to run before a multi-office set is signed off.

Where National Offices Still Diverge From European Practice

Validating or nationalising in Europe does not mean one drawing standard. The EPO has moved on colour; several national offices have not moved at all, and two of the busiest are now stricter than the EPO rather than aligned with it.

  • Germany. Annex 2 to the Patentverordnung (PatV) governs the national DPMA route and requires durable black lines without colours. It makes no provision for photographs at all, so the 37 CFR 1.84(b) “only practicable medium” escape hatch has no German counterpart. The usable illustration area is capped at 26.2 cm by 17 cm, and numerals and letters must be at least 0.32 cm high. See patent drawings in Germany.
  • Poland. Annex 1 to the ordinance of 17 September 2001 requires durable, black, intense and sharp lines, and WIPO’s PCT Applicant’s Guide chapter for Poland answers “No” to whether the office accepts colour under national law. Poland also sets a margin nobody else does: a 35 mm minimum left margin on drawing sheets, where the USPTO and the PCT both require 25 mm. See patent drawings in Poland.
  • Austria. Section 15 of the Patentverordnung (PAV) sets margins of 2 cm top, 2 cm left, 2 cm right and 2.5 cm bottom — a different shape from both Germany and the PCT, and the only one in this group with the largest margin at the foot of the sheet. The Austrian Patent Office treats colour tints and photographs as inadmissible and expresses its line rule as a 300 dpi reproduction test. Austria also asks for something no other office here does: the applicant’s name or file reference on the drawing sheet itself.
  • Ireland. Rule 12 and the IPOI’s formal requirements call for drawings “without colourings”. Ireland is also one of the EPC states that has closed its national PCT route, so there is no Irish national phase to enter — the way in is the European route.
  • Belgium. Belgium likewise has had no PCT national phase since 1 April 2018, and it does not carry out substantive examination. Figures are nonetheless part of the granted text and the disclosure.
  • The PCT itself. Rule 11.6 sets minimum margins on A4 sheets of 2.5 cm top, 2.5 cm left, 1.5 cm right and 1 cm bottom, with black line work under Rule 11.13(a).

The pattern worth internalising is that these standards disagree on geometry as well as on colour. Poland’s widest margin is on the left at 35 mm, Austria’s is at the bottom at 2.5 cm, Germany caps the usable area instead at 26.2 cm by 17 cm, and the PCT and USPTO share a fourth arrangement. There is no single sheet template that is simultaneously at the minimum for all of them — which is exactly why a template built for one office and reused silently for another is the most common source of formal objections we see.

The United States sits in a third position again. Under 37 CFR 1.84(g) the margins match the PCT figures; 37 CFR 1.84(p)(3) sets the same 0.32 cm character floor Germany and Poland use; 37 CFR 1.84(a)(2) permits colour drawings on a granted petition explaining why colour is necessary; and 1.84(b) permits photographs where they are the only practicable medium. Design cases answer to 37 CFR 1.152, which requires compliance with 1.84 plus enough views to constitute a complete disclosure of the appearance of the design.

Read together, the picture is simple enough to act on. Monochrome line work at 300 dpi, drawn to the tightest margin in the family and with characters at or above 0.32 cm, is accepted everywhere. Colour is a European-route option, not a family-wide one. Photographs are a US option, not a European one. Where a case is going to several offices, the cheapest sheet is the one drawn to the strictest member of the set — which, on margins, means Poland.

One documentation habit pays for itself. Record, per sheet, which standard it was drawn to and on what date — because the governing text now moves by presidential decision and OJ notice rather than by amendment to the Implementing Regulations, and a set drawn in 2022 was drawn against a rule that has since been deleted. When a divisional, a continuation or a validation comes back to the same figures three years later, that note is the difference between reusing the sheets and re-deriving the standard from scratch. It also answers the question an examiner or an opponent may eventually ask about why a particular figure looks the way it does.

If you need a set audited against more than one of these standards at once, our patent drawing service does that check per sheet before filing, which is the cheapest point in the process to catch a margin or character-height defect.

Need Compliant Patent Drawings?

Knowing the rules is one thing; producing figures that clear formalities review on the first pass is another. PerspireIP prepares professional patent drawings to USPTO 37 CFR 1.84 and 1.152, EPO Rule 46 EPC and PCT standards — a flat $25 per drawing whatever the complexity, delivered camera-ready in three to five business days and invoiced only after delivery.

Upload your sketches, photographs or CAD files (up to five) and tell us how many figures you need. We also work locally with filers in New York, San Jose, London, Munich and Paris.

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Frequently Asked Questions About Drawing guidelines

Conclusion

Formal drawing rules set precise formal standards that demand careful attention from both first-time European filers and experienced patent practitioners. From A4 paper and strict left margins to restrictions on text within drawings and reference sign consistency, every aspect of European patent drawings must be prepared with Rule 46 EPC in mind. Applicants who invest in compliant drawings before filing avoid formality examination delays that can set prosecution back by months.

PerspireIP attorneys are experienced in European patent prosecution and can guide you through every step of the EPO filing process. Contact us today to prepare drawings that meet EPO standards from the start. For more on formal patent drawing standards, explore our guide on patent drawing preparation.