Guide · The basics

Patent drawings: what they are and how to prepare them

Patent drawings are the sheets attached to a patent application: A4 pages with black line figures, numbered “FIG. 1, FIG. 2”, and reference numerals that point to the description. They make the invention understandable and follow the form rules of each office: EPO, PCT, USPTO and, in Italy, UIBM.

Updated October 2026 · Sources: OJ EPO 2025, A49, Rule 11 PCT, 37 CFR 1.84, Art. 22 D.M. 33/2010

The right words

Drawings, sheets and figures: three different things

Drawings

All the sheets of an application together. It is the legal term: the EPO lists request, description, claims, drawings and abstract as separate documents (Art. 2(3), OJ EPO 2025, A49), as does Art. 22 of Italy’s D.M. 33/2010.

Sheets

The individual A4 pages, numbered. Each sheet has a usable area bounded by the margins and can hold several figures.

Figures

The individual views: FIG. 1, FIG. 2, and FIG. 1A, FIG. 1B for partial views. They carry the reference numerals (reference signs).

In short: a patent application contains drawings; the drawings are made of A4 sheets; each sheet holds one or more figures. The same reference numeral identifies the same part in every figure, in the description and in the claims.

Types of figures

Which figures does a patent application need?

The figures must show what is needed to understand the invention. In the United States, 37 CFR 1.83(a) requires the drawing to show every feature specified in the claims.

Views and axonometric views

Orthographic views (front, side, top) and an axonometric view of the same object, often on the same sheet and at the same scale.

Sections

A section line marks the plane (A-A; at the EPO also XXII-XXII, Guidelines A-IX, 7.3.1). Hatching must not cover the reference numerals.

Exploded views and details

Separated parts show how the assembly fits together; enlarged details isolate a small area. In the US, an exploded view is enclosed in a bracket.

Flowcharts

For methods and software: numbered steps S100, S102… The EPO and the PCT treat them as drawings (Art. 1(3), EPO Decision 2025; Rule 7.1 PCT).

Block diagrams

For systems and circuits. In the US, conventional elements may be shown as labeled boxes (37 CFR 1.83(a)).

Photographs

An exception only: the EPO accepts them when the subject cannot be drawn (Guidelines A-IX, 1.2); the USPTO generally does not (1.84(b)).

Patent drawing sheet with four views of a valve, FIG. 3A, 3B, 3C and 3D, at the same scale, with reference numerals — Front, side, axonometric and top views on the same sheet (FIG. 3A–3D); FIG. 3D carries the section line A-A.

Patent drawing sheet with the hatched section A-A of a valve and the enlarged detail B — FIG. 4A: hatched section A-A with the detail circle B. FIG. 4B: detail B enlarged.

Patent flowchart of a method with steps S100 to S106 between START and END, FIG. 1 — Flowchart of a method, steps S100, S102…

Sheets exported from Inklaim with sample data.

Form rules

How do EPO, PCT, USPTO and UIBM drawing rules compare?

The rules are similar, but they are not the same. Knowing the differences saves you from redoing a sheet when the application moves from one office to another.

Rule	EPO	PCT	USPTO	UIBM (Italy)
Sheet	A4	A4	A4 or US Letter	A4
Margins (top / left / right / bottom)	2.5 / 2.5 / 1.5 / 1 cm	2.5 / 2.5 / 1.5 / 1 cm	2.5 / 2.5 / 1.5 / 1 cm	at least 2.5 cm on all sides
Height of numbers and letters	≥ 0.32 cm	≥ 0.32 cm	≥ 0.32 cm (1/8")	not specified (0.32 cm as good practice)
Sheet numbers	Arabic numerals, centered at the top	“1/3, 2/3, 3/3”	“1/3”, centered at the top	consecutive
Figure labels	“FIG”	Arabic numerals	“FIG.”	consecutive numbering
Color	electronic filing only, since 1 Oct 2025	published in black and white	only by petition	no, black lines
Text in drawings	indispensable words only	“a few short catchwords”	minimal legends	only what is needed for understanding, plus the scale (chamber of commerce practice)
Source	OJ EPO 2025, A49	Rule 11 PCT	37 CFR 1.84	Art. 22 D.M. 33/2010; Genoa Chamber of Commerce guide (secondary source, for text; in Italian)

The Italian margin

The UIBM asks for 2.5 cm on all sides: a sheet laid out for the EPO does not meet it to the letter. Since 1 January 2023, PDFs filed on the UIBM portal must be PDF/A (UIBM circular 621).

Color

The EPO accepts color and grayscale since 1 October 2025, but only online (OJ EPO 2025, A57). The International Bureau publishes PCT applications in black and white; the UIBM wants black lines.

Numbering

PCT and USPTO number the sheets “1/3”; the EPO uses consecutive Arabic numerals. The EPO writes “FIG”, the USPTO “FIG.” (37 CFR 1.84(u)).

The article-by-article detail is in the guide to EPO patent drawing requirements and in the guide to Italian patent drawings (UIBM).

The workflow

How to prepare patent drawings

In an IP firm, the draftsperson prepares the sheets and the patent attorney checks them against the text and approves them. These are the steps.

Gather the materialThe client’s 3D model (STEP, IGES), DXF or PDF technical drawings, sketches, the draft claims.
Choose the figuresThe views, sections and diagrams that show what is claimed. Nothing more.
SimplifyRemove dimensions, title block and unnecessary detail. Every detail must stay legible when reduced to 2/3.
NumberFIG. numbers in order of citation, and the same reference numerals in the text and in the figures.
Check and exportMargins, characters and text according to the office. PDF for filing, PDF/A for the UIBM.

How Inklaim helps

The same steps, without redrawing

Inklaim is web software from an Italian start-up founded in Turin that prepares draft patent drawings, checked against EPO, UIBM, USPTO, PCT, CNIPA and KIPO rules, from 3D CAD models (STEP/IGES), DXF or vector PDF files, photos of an object, sketches and claims.

Today, by hand

You redraw the views of the client’s model in a general-purpose CAD program.
You remove dimensions, texts and title block line by line.
You check the reference numerals by reading text and figures.
You renumber the figures and fix the references in the description.

With Inklaim

Views, A-A sections and exploded views from the STEP file, at the same scale.
DXF and PDF import that removes dimensions, texts, title block, center lines and hatching.
Consistency check across the whole matter, with a link to each error.
FIG. 1A, 1B and the references in the text updated automatically.

The geometry always comes from your files: AI is optional and does not draw. The final check and the filing stay with your firm. Learn more about patent drawing sheets from 3D models, simplifying patent figures, the reference numeral check and automatic figure numbering, or see all features.

FAQ

Questions about patent drawings

Can patent drawings be drawn by hand?

It depends on the office. The EPO requires black, uniformly thick and well-defined lines, generally drawn with drafting instruments (Art. 1(2)(a) and (e) of the Decision of 7 July 2025). For an Italian application, Art. 22 of D.M. 33/2010 also accepts drawings made by hand.

Can photographs be used instead of drawings?

Generally not. The EPO accepts them only when what must be shown cannot be drawn (Guidelines A-IX, 1.2); the USPTO only when they are the only practicable medium (37 CFR 1.84(b)).

Can the same sheet be used for the EPO and the Italian UIBM?

Not always. The EPO accepts 1.5 cm on the right and 1 cm at the bottom, while the UIBM asks for at least 2.5 cm on all sides. A sheet with 2.5 cm margins everywhere meets the minimums of both.

How tall must numbers and letters be?

At least 0.32 cm (1/8 inch) for the EPO, PCT and USPTO. The Italian regulation sets no value for drawings; 0.32 cm is normally used there too.