Paper sizes
A4, A3, A5.
Every A-series size comes from a sheet of one square metre (A0, 841 × 1189 mm) folded in half again and again. Because the sides are in the ratio 1 : √2, each size has exactly the same shape as the one before. The standard is ISO 216.
The logic of 1 : √2
If a rectangle has sides in the ratio 1 to √2 (1 : 1.414) and you cut it in half across the long side, both halves keep the same ratio. So an A3 is two A4s, an A4 is two A5s, and artwork scales from one size to the next without reflowing: A4 to A3 at 141 %, A3 to A4 at 71 %.
A0 (1 m²) folded in half again and again: A1, A2, A3, A4, A5…
The A series
| Size | Dimensions (mm) | Typical use |
|---|---|---|
| A0 | 841 × 1189 | Drawings, posters |
| A1 | 594 × 841 | Posters |
| A2 | 420 × 594 | Posters, wall calendars |
| A3 | 297 × 420 | Placemats, posters, A4 folded leaflets flat |
| A4 | 210 × 297 | Letterheads, leaflets, catalogues |
| A5 | 148 × 210 | Leaflets, books, notepads |
| A6 | 105 × 148 | Postcards, small pieces |
| A7 | 74 × 105 | Labels, small cards |
Each size is half the previous one. An A4 sheet of 80 g/m² weighs 5 g, because A4 is 1/16 of A0.
The B and C series, and DL
A series
The trimmed sizes of printed matter. A4 is the reference size in Europe.
B series
The geometric mean of two consecutive A sizes. B4 (250 × 353) and B5 (176 × 250) are used for books and posters.
C series and DL
C4 (229 × 324) takes an A4 flat, C5 (162 × 229) an A4 folded once, DL (110 × 220) an A4 folded in three.
Production sizes: SRA and the press sheet
A printed piece is not printed at its finished size. It is printed on a larger sheet, with 3 mm bleed around every item, trim marks and the margin the press needs to grip the paper. The SRA sizes (ISO 217) exist for exactly this: slightly larger than A, so the finished size can be trimmed cleanly. In offset, the press sheet (e.g. 70 × 100 cm) carries many copies at once, and their number sets the cost per piece.
| Size | Dimensions (mm) | Equivalent |
|---|---|---|
| SRA3 | 320 × 450 | A3 with bleed |
| SRA2 | 450 × 640 | A2 with bleed |
| SRA1 | 640 × 900 | A1 with bleed |
| 61 × 86 cm sheet | 610 × 860 | Offset sheet for medium runs |
| 70 × 100 cm sheet | 700 × 1000 | The standard offset sheet |
Tolerances and layout
Tolerances of the standard. ISO 216: ±1.5 mm up to 150 mm, ±2 mm from 150 to 600 mm, ±3 mm above 600 mm. Trimming at the printer is more accurate than that, but this is why the safe margin for text matters.
Design at the finished size. A 210 × 297 mm page for A4, with 3 mm bleed and text at least 4 mm inside the trim.
Scaling between sizes. A4 → A3: 141.4 %. A4 → A5: 70.7 %. Image resolution, however, must be sufficient at the larger size.
Letter is not A4. US Letter is 215.9 × 279.4 mm, wider and shorter. A file set up as Letter does not print correctly as A4. See the file specifications.
Frequently asked questions
Why is A4 210 × 297 mm?
Because it is 1/16 of a square metre with sides in the ratio 1 : √2. A0 is 841 × 1189 mm (1 m²), and each following size is made by folding it in half.
What is SRA3?
A 320 × 450 mm size (ISO 217), slightly larger than A3, so that an A3 can be printed with bleed and trimmed to its finished size.
What is the difference between A4 and Letter?
A4 is 210 × 297 mm; Letter is 215.9 × 279.4 mm (8.5 × 11 in). Letter is used in North America. For printing in Europe, files are set up as A4.
Send us the specifications of your job.
Size, quantity, material and number of colours. We reply with a technical proposal and a quote.