A3 Paper Size in CM: Dimensions, Comparisons & Chart

A3 paper measures exactly 29.7 cm × 42.0 cm, according to ISO 216—the international standard that governs paper sizes for most of the world. This specific dimension, roughly 11.7 × 16.5 inches, sits between standard office paper and large-format prints, making A3 the preferred size for detailed reports, architectural drawings, and professional presentations that need more visual space than A4 permits.

A3 Width: 29.7 cm · A3 Height: 42 cm · A3 Area: 0.125 m² · A3 in Inches: 11.7 × 16.5 in · ISO Standard: ISO 216

What is the A3 size in cm?

Exact dimensions

The official ISO 216 standard defines an A3 sheet as exactly 29.7 centimeters wide by 42.0 centimeters high. In millimeters, those dimensions translate to 297 mm × 420 mm—measurements that print designers and commercial shops work with daily. The surface area of a single A3 sheet comes to 0.125 square meters, which happens to be exactly one-eighth of the A0 base size that anchors the entire A-series hierarchy.

“The official ISO 216 standard for an A3 sheet of paper is exactly 29.7 centimetres wide by 42.0 centimetres high.” — Virtuall Blog, Design Blog

In mm and inches

For those working across measurement systems, A3 converts to 11.69 × 16.54 inches. Professional printing applications typically round this to 11.7 × 16.5 inches for practical use. At standard 300 DPI resolution, an A3 image requires 1754 × 2480 pixels for proper reproduction. The ISO 216 standard (Encyclopedia) allows manufacturing tolerances of ±2 mm for paper in the 150–600 mm dimension range.

Is 30x40cm A3?

Dimension comparison

A 30 × 40 cm sheet is close to A3 but not identical. True A3 is 29.7 × 42.0 cm, meaning the “30 × 40 cm” approximation undershoots width by 3 mm and overshoots height by 2 cm. For most casual purposes, 30 × 40 cm feels close enough, but in professional printing or precision framing, that gap becomes problematic. The Dimensions.com reference confirms these exact ISO 216 measurements.

Framing compatibility

Will an A3 sheet fit inside a 30 × 40 cm frame? The short answer: barely, and only with trimming or careful positioning. Since A3 is taller than it is wide (42 cm versus 29.7 cm), it won’t fit the 40 cm height comfortably within a frame meant for 30 × 40 cm oriented the other way. For proper A3 framing, you need at minimum a 30 × 42 cm opening, though 30 × 45 cm frames provide breathing room for mats.

“ISO 216 is an international standard for paper sizes, used around the world except in North America and parts of Latin America.” — Wikipedia, Encyclopedia

Which is bigger, an A3 or an A4?

A3 vs A4 sizes

A3 is significantly larger than A4—exactly twice the area, in fact. While A3 measures 297 × 420 mm, A4 comes in at 210 × 297 mm, making it precisely half the dimensions when folded. This relationship isn’t accidental: the ColorCopiesUSA printing guide explains that ISO 216’s √2 aspect ratio means every A-size folds perfectly into the next smaller one. Two A4 sheets placed side by side equal one A3 with no wasted paper or odd margins.

“The ISO 216 standard uses the √2 (1.414) aspect ratio, which means when you fold any size in half, you get the next smaller size with the same proportions.” — ColorCopiesUSA, Printing Guide

Practical differences

In everyday terms, A4 is the standard office and printer paper size most of the world uses for documents, letters, and homework. A3 sits in a different category—it’s the size of broadsheet newspaper pages, detailed architectural drawings, and professional design presentations. The Wikipedia overview notes that A4 is the most commonly available paper size worldwide, while A3 typically requires special ordering or dedicated large-format copiers.

What is A1, A2, A3, and A4?

A series overview

The A-series defined by Pixartprinting (Commercial print vendor) follows a simple mathematical logic: A0 defines the starting point at exactly 1 square meter, and every subsequent number halves the area. A1 is 59.4 × 84.1 cm, A2 is 42 × 59.4 cm, A3 is 29.7 × 42 cm, and A4 is 21 × 29.7 cm. The series continues down through A5 (14.8 × 21 cm) and beyond, though smaller sizes see diminishing practical use.

Size progression

The ANSI Blog (Standards organization) confirms that A4 is half of A3, and A3 is half of A2. This halving property means that an A2 sheet, when cut exactly in half along its longer edge, produces two A3 sheets with identical proportions. The aspect ratio stays constant at 1:√2 (approximately 1:1.414) because the √2 ratio has the unique property of remaining unchanged when a rectangle is halved along its longer side.

The table below shows how the A-series sizes relate through the halving property that defines ISO 216.

What this means: each step down the A-series halves the surface area while maintaining the √2 aspect ratio that keeps proportions consistent across all sizes.

What’s bigger, A1, A2, A3, A4, and A5?

Full A series ranking

The hierarchy runs clearly from largest to smallest: A1 exceeds A2, A2 exceeds A3, A3 exceeds A4, and A4 exceeds A5. The Neenah Paper resource (Paper manufacturer) provides the full A-series table showing A1 at 59.4 × 84.1 cm, A2 at 42 × 59.4 cm, A3 at 29.7 × 42 cm, and A5 at 14.8 × 21 cm. The area halves with each step down the series, making size comparisons straightforward.

Common uses

Each A-series size serves distinct practical purposes. A1 and A0 dominate technical drawings, engineering blueprints, and large format posters. A2 handles small posters and detailed art prints. A3—your target size—covers magazines, professional reports, and presentations that need more visual space than A4 permits. A4 handles everyday documents, while A5 suits notebooks, flyers, and promotional postcards. The Virtuall Blog (Design resource) notes that A3’s printing standard status makes it essential for anyone producing materials for international distribution.

Related reading: standard size charts

A3 measures precisely 29.7 by 42 cm under ISO 216 standards, where detailed A3 cm comparisonsdelve into side-by-side charts with A4, A2, and inches equivalents.

Frequently asked questions