Patent drawing requirements: USPTO, EPO and India

USPTO, EPO and India side by side

"A-IX" refers to Part A, Chapter IX of the EPO Guidelines for Examination (2026 edition). Indian rules are from the Patents Rules, 2003.

The practical point: a sheet laid out for the USPTO will usually work at the EPO, because the margins and the 0.32 cm letter height are the same. It will not meet rule 15 in India without moving the figures inward and adding the applicant's name, sheet count and signature.

USPTO: 37 CFR 1.84 and the rules around it

When drawings are required

The applicant must furnish a drawing where necessary to understand the invention (35 U.S.C. 113, 37 CFR 1.81(a)). Flow sheets for processes and diagrammatic views count (1.81(b)). If the subject matter admits of illustration and no drawing was filed, the examiner will require one within at least two months (1.81(c)). Drawings filed after the filing date cannot cure an inadequate disclosure (1.81(d)).

In a nonprovisional application the drawings must show every feature specified in the claims (37 CFR 1.83(a)). Conventional features whose detail is not essential can be shown as a graphical symbol or a labeled rectangular box. The description must briefly describe each view and refer to parts by reference numerals (37 CFR 1.74).

Sheets, margins and lines

• Ink: black and white drawings in India ink or an equivalent that gives solid black lines (1.84(a)(1)). Every line, number and letter must be clean, dense and uniformly thick (1.84(l)).
• Sheet size: 21.0 × 29.7 cm (A4) or 21.6 × 27.9 cm (8.5 × 11 inches), with every sheet in the application the same size (1.84(f)).
• Margins: at least 2.5 cm top, 2.5 cm left, 1.5 cm right and 1.0 cm bottom, leaving a usable area of no more than 17.0 × 26.2 cm on A4. No frame around the usable area (1.84(g)).
• Scale: large enough to read when reduced to two-thirds. Notes such as "actual size" or "scale 1/2" are not permitted (1.84(k)).
• Shading: encouraged where it helps and stays legible. Spaced thin lines are preferred, with light from the upper left at 45°. Solid black areas are not permitted except for bar graphs or to represent color (1.84(m)).
• Cross sections: regularly spaced oblique hatching, preferably at 45°, that does not obscure reference characters (1.84(h)(3)).

Views, numerals and lead lines

• Views: as many as needed: plan, elevation, section, perspective, exploded and detail views. No projection lines or center lines, and one view must not sit inside another (1.84(h), (i)).
• View numbers: consecutive Arabic numerals preceded by "FIG.", larger than the reference numerals. Partial views of one figure take a capital letter (FIG. 1A, FIG. 1B). A single view is not numbered and carries no "FIG." (1.84(u)).
• Sheet numbers: two numerals either side of a slash, such as "2/5", centered at the top inside the usable area (1.84(t)).
• Reference characters: numerals are preferred, at least 0.32 cm high, not circled or bracketed. The same part always takes the same numeral and one numeral never names two parts. Numerals not in the description must not appear in the drawings, and numerals in the description must appear in them (1.84(p)).
• Lead lines: as short as possible, starting next to the numeral and ending at the feature, never crossing each other. A numeral without a lead line, placed on the surface it names, is underlined (1.84(q)).

Photographs and color

Photographs are accepted only where they are the only practicable medium, such as electrophoresis gels, blots, cell cultures, histology sections or crystal structures (1.84(b)(1)). Color drawings or color photographs in a utility application need a granted petition under 1.84(a)(2) that explains why color is necessary. The petition includes the 37 CFR 1.17(h) fee of $150 ($60 for a small entity, $30 for a micro entity), one set of color drawings if filed through Patent Center, and a set paragraph added at the start of the brief description of the drawings stating that the file contains at least one drawing executed in color.

Replacement sheets

Any change to a drawing is filed on a full replacement sheet labeled "Replacement Sheet" in the top margin, carrying every figure that was on the earlier version of that sheet, even if only one changed. An added figure goes on a sheet labeled "New Sheet". The changes must be explained in the amendment or the remarks, and a marked-up copy may be included as an "Annotated Sheet" (37 CFR 1.121(d)). No amendment may add new matter (1.121(f)). Unless the examiner says otherwise, drawing objections are not held in abeyance, and corrected drawings required at allowance are due within a non-extendable three months of the notice of allowability (37 CFR 1.85(a), (c)).

EPO: what replaced Rule 46 EPC

Most guides still cite Rule 46 EPC. It was deleted with effect from February 1, 2023 (CA/D 10/22), and Rule 49(2) EPC now leaves presentation to the President of the EPO. For documents filed on or after October 1, 2025 the requirements are in the decision of July 7, 2025 (OJ EPO 2025, A49), which replaced the decision of November 25, 2022 (OJ EPO 2022, A113). The practice is explained in Guidelines A-IX. Most of the old Rule 46 text carried over.

• When drawings are needed: the application contains any drawings referred to in the description or claims (Art. 78(1)(d) EPC), and the description briefly describes each figure (Rule 42(1)(d)). If drawings referred to are missing, the EPO invites you to file them, and the application is re-dated to the day they arrive unless they are completely contained in the priority application (Rule 56 EPC).
• Margins: at least 2.5 cm top, 2.5 cm left, 1.5 cm right and 1 cm bottom, with a usable area of no more than 26.2 × 17 cm and no frame (A-IX, 4.1).
• Color: black and white remains the default. Since October 1, 2025, color and greyscale drawings are admissible in applications filed electronically, and must be clear at 300 dpi (A-IX, 2.2 and 7.1; OJ EPO 2025, A57). Paper filings and earlier applications are published in black and white. The EPO advises against describing features by color in the description or claims (A-IX, 7.5.4).
• Figures: numbered in Arabic numerals preceded by "FIG", independently of the page numbers. A single figure is not numbered. Figures that do not fit upright are turned with their top on the left of the page (A-IX, 5.1 and 5.2).
• Page numbers: centered at the top within the usable area, not in the margin. The drawings preferably have their own series starting at 1 (A-IX, 4.2).
• Lines and lettering: drawn with drafting instruments where one exists, letters and numbers at least 0.32 cm high, no brackets, circles or inverted commas around them, readable at two-thirds reduction (A-IX, 7.1, 7.4, 7.5 and 7.5.3).
• Reference signs: reference signs not mentioned in the description and claims may not appear in the drawings, and the other way round. The same feature keeps the same sign throughout. For variants, numbering such as 115 in FIG. 1 and 215 in FIG. 2 is accepted if the description explains it (A-IX, 7.5.4 and 7.5.5).
• Signs in claims: where the application has drawings with reference signs, claimed features should preferably be followed by those signs in parentheses. They do not limit the claim (Rule 43(7) EPC).
• Text: none unless indispensable, and then a few words with space left around them for translation (A-IX, 8).

Amended drawings must not extend the content of the application as filed (Art. 123(2) EPC). That includes color drawings filed to replace black-and-white originals (A-IX, 10). For PCT applications entering the European phase, the EPO uses color drawings only if they are available on PATENTSCOPE and the international publication refers to them (OJ EPO 2025, A57).

India: rule 15 of the Patents Rules

Drawings may be supplied with any specification, provisional or complete, and must be if the Controller requires them. Once supplied they form part of the specification (section 10(2)). Where the invention needs explaining through drawings, they are prepared under rule 15 and referred to in detail in the specification (rule 13(4)). Rule 15 itself is short:

• Drawings accompany the specification they relate to, and no drawing appears inside the specification text (rule 15(1), (2)).
• A4 sheets with a clear margin of at least 4 cm at the top and left and 3 cm at the bottom and right (rule 15(4)).
• A scale large enough to show the invention clearly, with no dimensions marked (rule 15(5)).
• Drawings numbered sequentially or systematically. Each sheet carries the applicant's name in the top left corner, the total number of drawing sheets and the sheet's own number in the top right corner, and the signature of the applicant or the agent in the bottom right corner (rule 15(6)).
• No descriptive matter on the drawings, except in flow diagrams (rule 15(7)).

India is stricter than the US and the EPO on reference signs in claims: rule 13(4) says claimed features illustrated in the drawings "shall be followed by their respective reference signs in parentheses". The abstract names the figure to be published with it, and each main feature mentioned in the abstract takes its reference sign (rule 13(7)(d)). A complete specification can adopt the drawings filed with the provisional by referring to them (rule 13(4)). Amended drawings are filed as retyped pages with a marked copy and a statement of what changed and why (rule 14). For the filing steps around this, see how to file a patent in India.

Common reasons drawings are objected to

USPTO examiners raise these with the form paragraphs in MPEP 608.02; the EPO equivalents are in Guidelines A-IX.

1. A claimed feature is not shown. The fix is to add the feature to a figure without adding new matter, or to cancel it from the claims (37 CFR 1.83(a), form paragraph 6.36).
2. Reference numerals do not match the text. A numeral in a figure that the description never mentions, or one in the description that no figure shows (1.84(p)(5), form paragraphs 6.22.06 and 6.22.07; A-IX, 7.5.4). This often follows an amendment that deleted a paragraph.
3. One part, two numerals, or one numeral, two parts. (1.84(p)(4), form paragraphs 6.22.02 and 6.22.03; A-IX, 7.5.5.)
4. Lines too light or too fine to reproduce. Gray, antialiased or thin lines that blur at two-thirds reduction (1.84(k), (l); form paragraph 6.26 where the drawings are not good enough to examine).
5. Color or photographs without a reason. At the USPTO, without a granted petition (form paragraph 6.24.01). At the EPO, color in a paper filing is published in black and white, and any detail that depended on it is lost.
6. Unlabeled boxes and too much text. A block diagram of empty rectangles does not show the claimed elements; label them (1.83(a)). At the EPO the opposite problem is common: sentences inside figures where a reference sign would do (A-IX, 8).
7. Circled numerals, frames and wrong labels. Numerals in circles or brackets, frames around the usable area, and "Figure 1" or "Fig-1" instead of FIG. 1 (1.84(g), (p)(1), (u)).
8. US sheets filed in India unchanged. Margins under 4 cm and 3 cm, and no applicant name, sheet count or signature (rule 15(4), (6)).

Flowcharts and block diagrams

All three offices treat them as drawings. The USPTO lists flow sheets for processes and diagrammatic views as permitted illustrations (37 CFR 1.81(b)), and allows a conventional element to be shown as a labeled rectangular box (1.83(a)). The EPO deems flow sheets and diagrams to be drawings (A-IX, 1.1). India's rule 15(7) makes flow diagrams the one place descriptive matter is allowed.

• Give each box and each step a reference numeral (for example 100 for the system, 102 and 104 for its components, S202 or 202 for method steps) and use the same numerals in the detailed description.
• Keep labels short. The EPO allows more than a few words for method steps, "such as a short sentence" per step, because the graphic alone may not convey the step (A-IX, 8). The USPTO asks for legends with as few words as possible (1.84(o)).
• Text, numerals and arrows follow the same rules as any other drawing: black, at least 0.32 cm high, readable when reduced to two-thirds, and laid out so the sheet does not need rotating.
• A common layout for a software or method application pairs a system block diagram with one flowchart per independent method claim, so that each claimed step appears in a figure.

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