A paper sizes: A0 to A10 in mm and inches

A series size chart

Sizes are given as width by height of an upright sheet. The smaller the number, the larger the sheet.

How to use the chart

Find the size name in the first column and read across. Use the millimetre values when you order paper, frames or print work: they are the defined sizes. The inch values are rounded conversions and are only there for comparison.

• A4 is the ordinary office sheet in most countries.
• A3 is two A4 sheets side by side.
• A5 is an A4 sheet folded once.
• A6 is an A4 sheet folded twice.

For a landscape sheet, swap width and height. The size name stays the same.

How the sizes are derived

The series is defined by the international standard ISO 216 and follows three rules.

1. A0 has an area of one square metre.
2. The long side is the short side multiplied by the square root of 2, about 1.414. A sheet with this shape keeps its proportions when it is cut in half.
3. Each next size is the previous one cut in half across its long side, rounded down to the whole millimetre.

The first two rules give A0 as 841 mm by 1189 mm. Halving the long side gives A1: 1189 divided by 2 is 594.5, rounded down to 594, so A1 is 594 mm by 841 mm. The chart on this page is calculated this way and was then compared with the table in the standard.

Because of the rounding, the calculated areas are a little smaller than the exact fractions of a square metre.

Worked example: weight of a letter

Paper weight is stated in grams per square metre. Since A0 is one square metre, a sheet of A0 in 80 gram paper weighs 80 grams.

A4 is one sixteenth of A0. One sheet of 80 gram A4 paper therefore weighs 80 divided by 16, which is 5 grams. Four sheets weigh 20 grams before you add the envelope.

The same rule explains copier settings. Enlarging A4 to A3 doubles the area, so each side grows by the square root of 2: set the copier to 141 percent. Reducing A3 to A4 needs 71 percent.

Common mistakes

• Treating A4 and Letter as the same. Letter is 8.5 by 11 inches: wider and shorter than A4.
• Ordering by the rounded inch values. A frame sold as 8.27 by 11.69 inches is an A4 frame; a frame sold as 8.5 by 11 inches is not.
• Assuming a larger number means a larger sheet. A3 is twice the size of A4.
• Confusing A sizes with B sizes or with C envelopes. B5 and A5 are different sheets.
• Expecting exact cuts. Finished sheets may differ slightly from the nominal size within the tolerance of the standard.

• A4 compared with Letter
• B series paper sizes

Sources and checks

The values in the chart are calculated from the definitions in the sources below. They are not copied from another chart. Last checked against the sources on September 28, 2026.

Sizes are trimmed sheet sizes. Millimetre values are the nominal sizes of the standard; inch values are conversions at 25.4 mm per inch, rounded to two decimals.

The calculated millimetre values were compared with Table 1 of the ISO 216:2007 preview and match for A0 to A10.

Tolerances are reported from a secondary source because the tolerance clause is not part of the public preview: 1.5 mm up to 150 mm, 2 mm up to 600 mm and 3 mm above.

• ISO 216:2007, Writing paper and certain classes of printed matter: trimmed sizes, A and B series (ISO catalogue entry)

Used for: Title, edition and status of the standard that defines the A and B series.

• ISO 216:2007 preview, clauses 1 to 6 (iTeh Standards sample)

Used for: Halving principle, side ratio of 1 to the square root of 2, A0 area of one square metre, B sizes as geometric means, and the millimetre values of A0 to A10 and B0 to B10 used to check the calculation.

• Markus Kuhn, International standard paper sizes (University of Cambridge Computer Laboratory)

Used for: Rounding down to the millimetre after each halving, the tolerances of ISO 216, the C series as geometric mean of A and B, and which sheet fits which envelope.