Is A3 bigger than A4?

Yes — A3 is exactly twice the area of A4. A3 is 297 × 420 mm and A4 is 210 × 297 mm. Fold an A3 in half along its long edge and you have an A4, at exactly the same proportions.

The reason it trips people up is that A-series numbering runs backwards: the smaller the number, the bigger the sheet. A0 is the largest and A10 the smallest. Once you know that, the rest of the series follows.

A3 against A4

	Millimetres	Centimetres	Inches
A3	297 × 420 mm	29.7 × 42.0 cm	11.69 × 16.54 in
A4	210 × 297 mm	21.0 × 29.7 cm	8.27 × 11.69 in

Two A4 sheets side by side make an A3. Two A3 sheets make an A2. The ratio of every A size is 1 : √2, which is why artwork scales between them without anything being cropped or stretched.

What each size is used for

A0 — 841 × 1189 mm

The largest despite the lowest number, and over a metre tall — the same area as sixteen sheets of A4. Used for large signs, trade show graphics and cinema-style posters. A0 is exactly one square metre, which is where the series starts and why paper weight is quoted in gsm: a sheet of A0 in 80gsm paper weighs exactly 80 grams.

A1 — 594 × 841 mm

Signs, window displays, event posters, seating charts and exhibition boards. About the span of an adult's shoulders across.

A2 — 420 × 594 mm

Notices, posters, art prints and window cards. Slightly larger overall than a broadsheet newspaper.

A3 — 297 × 420 mm

The size you meet at work and school. Posters, plans, charts, presentations, counter signage and table menus. Not a standard home size, but most business inkjets handle it and some A4-footprint machines print it.

A4 — 210 × 297 mm

The everyday sheet, used throughout Australia for documents, letterheads and flyers. Every laser and inkjet printer takes it.

A5 — 148 × 210 mm

Flyers, invitations, booklets, planners and diaries — anything handed to a person rather than hung on a wall. Half of A4, so two A5s print on one A4 sheet.

A6 — 105 × 148 mm

Postcards, leaflets, loyalty cards and save-the-dates. Too small for long text, ideal in the hand.

Paper size chart

The A series runs down to a tiny A10. Millimetres are the definition under ISO 216 and are exact; centimetres and inches are converted from them.

Paper	Millimetres	Centimetres	Inches
A0	841 × 1189 mm	84.1 × 118.9 cm	33.11 × 46.81 in
A1	594 × 841 mm	59.4 × 84.1 cm	23.39 × 33.11 in
A2	420 × 594 mm	42.0 × 59.4 cm	16.54 × 23.39 in
A3	297 × 420 mm	29.7 × 42.0 cm	11.69 × 16.54 in
A4	210 × 297 mm	21.0 × 29.7 cm	8.27 × 11.69 in
A5	148 × 210 mm	14.8 × 21.0 cm	5.83 × 8.27 in
A6	105 × 148 mm	10.5 × 14.8 cm	4.13 × 5.83 in
A7	74 × 105 mm	7.4 × 10.5 cm	2.91 × 4.13 in
A8	52 × 74 mm	5.2 × 7.4 cm	2.05 × 2.91 in
A9	37 × 52 mm	3.7 × 5.2 cm	1.46 × 2.05 in
A10	26 × 37 mm	2.6 × 3.7 cm	1.02 × 1.46 in

Will it be readable? The lettering rule

Most people asking whether A3 is bigger than A4 are really asking which one their sign should be. Work back from the viewing distance: about 25 mm of capital letter height per metre.

Read from	Minimum cap height	Fits comfortably on
1 m	25 mm	A4, A3
3 m	75 mm	A2, A1
5 m	125 mm	A1, A0
10 m	250 mm	A0 and larger, or a banner

A headline that fails this rule on an A3 does not get fixed by printing it on A2 — it gets fixed by using fewer words.

Printing bigger than A3?

That is where we come in. Paper is fine indoors and behind glass; outdoors it does not last a week. Our standard corflute sign is 600 × 900 mm — within a few millimetres of A1 — and it is waterproof and rigid, so it works on a gate, a fence or a shop window. For an entrance, a pull up banner is 800 × 2000 mm and stands up by itself. For a footpath, an A-frame sign takes a replaceable insert. Past A0, a sheet stops being practical and fabric or vinyl banners are what scale.

Everything is printed in our own Melbourne factory and dispatched within 24 hours of proof approval. You can add your own wording to a ready-made design online for free, or send print-ready artwork. Custom sizing is available if none of the standard sizes fit.

Related: A1 size in cm · A5 size in cm · A1 vs A2 vs A3 · Common poster sizes in Australia