PCT Drawing Requirements: 7 Essential Rules for 2026

A single drawing sheet with a 0.2 cm reference numeral can cost you two months and a formal objection. Most inventors treat figures as an afterthought and discover, well after filing, that the PCT drawing requirements are a genuine formality regime with teeth: the receiving Office checks them, the International Bureau publishes from them, and every national office you enter later inherits whatever you filed. The rules themselves are not difficult. They are just unforgiving, and they have moved twice in the last three years on the European side.

PCT Drawing Requirements Start and End With Rule 11

There is no separate drawing chapter in the Patent Cooperation Treaty. Everything sits in Rule 11 of the Regulations under the PCT, titled “Physical Requirements of the International Application.” Rule 11.10 through 11.13 do the real work for figures.

That single-source structure is why the PCT drawing requirements feel deceptively simple. One rule covers paper, margins, line weight, hatching, scale, lettering, and reference signs for every one of the 150-plus PCT Contracting States. Get Rule 11 right once and the international phase stops being a formalities risk.

One framing point matters before the details. Rule 11 is a publication standard, not a quality standard. The International Bureau needs figures that reproduce legibly at scale across every published application. Read the rules that way and most of them stop looking arbitrary.

Rule 1: Sheet Size, Margins, and Usable Surface

Rule 11.5 requires A4 sheets — 29.7 cm x 21 cm. A receiving Office may accept other sizes, but the record copy that reaches the International Bureau has to be A4, so filing on US letter simply moves the conversion problem downstream.

Rule 11.6 sets the minimum margins. For sheets containing drawings they are tighter than for the text pages:

• Top: 2.5 cm
• Left side: 2.5 cm
• Right side: 1.5 cm
• Bottom: 1 cm

Those four numbers are identical to the US margins in 37 CFR 1.84(g), which is a small mercy: one drawing set can satisfy both regimes. The usable surface on a drawing sheet must not exceed 26.2 cm x 17.0 cm.

Rule 11.10 also requires drawings to sit on their own sheets. They may not be embedded in the description, the claims, or the abstract. Engineers who build a specification in a word processor with inline figures trip this constantly.

Rule 2: Line Quality, Hatching, and Scale

Rule 11.13(a) is the provision that rejects the most figures. Drawings “shall be executed in durable, black, sufficiently dense and dark, uniformly thick and well-defined, lines and strokes without colorings.” Every word there is load-bearing. Grey CAD hairlines fail on density. Anti-aliased raster exports fail on “well-defined.” Screenshots almost always fail.

Rule 11.13(b) requires cross-sections to be indicated by oblique hatching that does not impede the clear reading of the reference signs. In practice that means breaking the hatch pattern where a numeral sits, rather than running a lead line across dense diagonal fill.

Rule 11.13(c) governs scale, and it is the rule people misread. The figure must be drawn so that a photographic reproduction reduced linearly to two-thirds size still distinguishes all details. So the test is not whether your figure looks clear on a monitor. It is whether it survives a 33% reduction.

The practical consequence: crowd less onto each sheet. A dense assembly view that reads fine at full size turns into a smudge at two-thirds, and the receiving Office is entitled to say so.

Rule 3: Reference Signs, Lettering, and Text Matter

Rule 11.13(h) sets a hard floor: “The height of the numbers and letters shall not be less than 0.32 cm.” That is the same 1/8 inch minimum the USPTO applies under 37 CFR 1.84(p)(3). Eight-point type in a CAD export is roughly 0.28 cm and quietly fails.

Rule 11.13(m) requires consistency: the same features, when denoted by reference signs, must be denoted by the same signs throughout the international application. A part that is element 12 in Figure 1 cannot become element 120 in Figure 6, and a numeral in the drawings that never appears in the description is a defect that follows you into every national phase.

Rule 11.11 handles words. Drawings “shall not contain text matter, except a single word or words, when absolutely indispensable” — the rule’s own examples are terms such as “water,” “steam,” “open,” and “closed.” Flowcharts and state diagrams get a practical exception because the boxes cannot be understood otherwise, but a labelled mechanical assembly does not.

Why is the rule so hostile to text? Translation. Every word inside a figure has to be translated for each national phase, and text baked into a raster image cannot be. Keep the labels in the description and the numerals in the drawing.

Rule 4: Colour and Photographs Are Still Restricted

Rule 11.13(a)’s phrase “without colorings” means what it says. The PCT drawing requirements do not accommodate colour figures in the international phase, and colour that survives your national filing will generally be converted to greyscale for international publication.

Photographs are a subtler point. Rule 11 makes no express provision for them at all. In practice, receiving Offices and the International Bureau accept photographs where the subject matter genuinely cannot be shown in a line drawing — crystalline structures, cell cultures, metallurgical grain — provided they reproduce adequately in black and white. Treat that as tolerated practice, not an entitlement, and file line drawings wherever a draftsperson could plausibly produce one.

The US position is stricter and better documented. Under 37 CFR 1.84(b)(1), photographs are permitted only when they are the only practicable medium for illustrating the claimed invention, and 37 CFR 1.84(a)(2) requires a petition, the fee under § 1.17(h), and a specific amendment to the specification before colour drawings are accepted at all. Our guide to color patent drawings walks through that petition.

Rule 5: The EPO Rules Moved — Rule 46 EPC Is Gone

If you are working from a guide that cites Rule 46 EPC for European drawing formalities, that guide is out of date. As part of the EPO’s digital transformation package, Rule 46 EPC was deleted, along with Rule 49(3)-(12) EPC, with effect from 1 February 2023. Rules 49(2), 50, 57(i) and 82(2) EPC were adapted at the same time.

The substance did not vanish. It moved into a Decision of the President of the EPO published in the Official Journal, so that the EPO can adjust presentation requirements as filing technology changes without amending the Implementing Regulations. The first decision largely restated the deleted text.

Then the substance itself changed. From 1 October 2025, the EPO permits drawings filed by electronic communication to be executed in colour or greyscale, provided they are sufficiently rich in contrast and suitable to be displayed clearly at 300 dpi. Colour is limited to the drawings — the description, claims, and abstract stay black and white.

Here is the trap for Euro-PCT cases, and it is a real one. That EPO concession does not amend the PCT. Rule 11.13(a) still bars colour in the international phase, and where the EPO acts on a Euro-PCT application it will work from the colour version only if colour drawings are available on PATENTSCOPE and the international publication says so. Otherwise the black-and-white version governs. Filing colour into the international phase and hoping the EPO picks it up later is not a strategy. See our EPO drawing requirements guide for the European side in detail.

Rule 6: How PCT Drawing Requirements Map to the US National Phase

Entering the US national phase does not re-open your figures for free. The USPTO applies 37 CFR 1.84, and while it overlaps heavily with Rule 11, the differences bite:

• Sheet size: 37 CFR 1.84(f) allows either 21.0 cm x 29.7 cm (A4) or 21.6 cm x 27.9 cm (letter). The PCT allows only A4.
• Margins: identical to Rule 11.6 — 2.5 cm top and left, 1.5 cm right, 1.0 cm bottom.
• Line character: 37 CFR 1.84(l) requires every line, number, and letter to be durable, clean, black, sufficiently dense and dark, and uniformly thick and well-defined.
• Lettering: 37 CFR 1.84(p)(3) sets the same 0.32 cm minimum height as Rule 11.13(h).
• Colour: 37 CFR 1.84(a)(2) requires a petition, a fee, and a specification amendment. There is no equivalent petition route in the international phase.

One structural point that saves people from a wasted week: you cannot obtain a US design patent through the PCT. The Treaty covers patents for invention, and industrial designs run through the Hague System instead. So 37 CFR 1.152 — which requires a design to be represented by drawings complying with § 1.84, with a sufficient number of views for a complete disclosure, appropriate surface shading, and broken lines used only for visible environmental structure rather than hidden planes — never applies to a national-phase entry from a PCT application.

If your invention has both a functional and an ornamental story, that means two filing tracks from the start. Our breakdown of 37 CFR 1.84 covers the US side view by view.

Rule 7: What Happens When the Receiving Office Objects

This is the part most guides omit, and it is the part that determines whether a defect is an inconvenience or a disaster.

Under PCT Article 14(1)(a)(v), the receiving Office checks whether the international application complies, to the extent provided in the Regulations, with the prescribed physical requirements. If it finds a defect, Article 14(1)(b) requires it to invite you to correct — and if you do not, the application “shall be considered withdrawn.” Rule 26.2 gives you two months from the date of the invitation, extendable by the receiving Office before it takes a decision.

The saving grace is Rule 26.3. The receiving Office checks Rule 11 compliance only to the extent that compliance is necessary for the purpose of reasonably uniform international publication. That is a deliberately forgiving standard. A margin that is 2.3 cm instead of 2.5 cm will usually pass; figures that reproduce as grey mush will not.

Do not read that leniency as permission to file sloppy drawings. A defect the receiving Office waives at the international stage is still sitting in the file when you enter each national phase, and offices applying their own domestic standards are under no obligation to be as forgiving. Fixing figures once, before filing, is cheaper than fixing them in six jurisdictions.

A Pre-Filing Checklist That Catches Most Defects

Run these seven checks on every sheet before the application leaves your desk. They map directly onto the PCT drawing requirements above and catch the overwhelming majority of Article 14 invitations:

1. A4 sheets, margins of 2.5 / 2.5 / 1.5 / 1.0 cm, usable surface within 26.2 cm x 17.0 cm.
2. Solid black line work, uniform thickness, no greyscale fills, no anti-aliased raster output.
3. Print the sheet at two-thirds size and confirm every detail is still distinguishable.
4. Every numeral at least 0.32 cm high, and legible where it meets hatching.
5. Every reference sign consistent across all figures and present in the description.
6. No text matter beyond genuinely indispensable single words.
7. Drawings on their own sheets, numbered consecutively, separate from the description and claims.

A draftsperson who works to Rule 11 daily will clear this list without thinking about it. The cost of that work is trivial next to a two-month formalities delay on a case with a live priority deadline.

This article is general information, not legal advice; consult a qualified attorney for your situation.

How PerspireIP Can Help

PerspireIP produces international-phase figures to Rule 11 and national-phase sets to 37 CFR 1.84 and current EPO practice, from CAD files, prototypes, sketches, or a written description. Every set is checked against the publication standard the receiving Office actually applies, not a generic template. See our patent drawing services, or contact us with your figures and filing deadline for a fixed quote.

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