Pixels
A4 measures 210 × 297 mm (8.27 × 11.69 in). At 300 DPI that is 2480 × 3508 pixels, and in a PDF 595 × 842 points. It is the standard office and school sheet almost everywhere outside North America; at 80 g/m² one sheet weighs about 5 g, since A4 is 1/16 of a square meter.
How to use
- Pick a series (ISO A, US, B, envelopes, photos, cards) and tap a size.
- The drawing shows the size to scale next to a comparison sheet; change the comparison or switch between portrait and landscape.
- Tap any row to copy the size in mm, cm, inches, points or pixels.
- Under Pixels, choose 72, 96, 150, 300 or 600 DPI or type your own. The choice is remembered.
- ISO A, B and C sizes all have the ratio 1 : √2, so halving a sheet gives the next size with the same shape. A0 is one square meter.
- Japan's JIS B sizes are slightly larger than ISO B: JIS B5 is 182 × 257 mm, ISO B5 is 176 × 250 mm.
- Use 300 DPI for print, 150 DPI for draft or large posters, and 72 or 96 DPI for screens. Points (1/72 in) are the unit in PDF and InDesign.
- C envelopes fit the matching A sheet: an A4 sheet goes flat into C4, folded once into C5 and twice into C6 or DL.
How ISO 216 paper sizes work
A sizes all share the ratio 1 : √2, so cutting a sheet in half across its long side gives the next size with the same shape. A0 is defined as one square meter (841 × 1189 mm); A1 is half of that, A4 is one sixteenth and measures 210 × 297 mm. B sizes sit between A sizes, and C sizes are for envelopes that hold the matching A sheet.
North America uses inch-based sizes instead: Letter 8.5 × 11 in, Legal 8.5 × 14 in and Tabloid 11 × 17 in. Letter is a little wider and shorter than A4, which is why documents sometimes get cropped when printed across the two systems.
From millimeters to pixels
Pixels depend on resolution: pixels = mm ÷ 25.4 × DPI. Use 300 DPI for print (A4 is 2480 × 3508 px), 150 DPI for drafts and large posters viewed from a distance, and 96 DPI for on-screen layouts. PDF and design software measure in points, 72 to the inch, so A4 is 595 × 842 pt.
Frequently asked questions
What size is A4 in cm and inches?
A4 is 21 × 29.7 cm, or 8.27 × 11.69 inches (210 × 297 mm).
Is Letter the same as A4?
No. Letter is 215.9 × 279.4 mm, A4 is 210 × 297 mm: Letter is 5.9 mm wider and 17.6 mm shorter.
How many pixels is A4 at 300 DPI?
2480 × 3508 pixels. At 150 DPI it is 1240 × 1754 and at 72 DPI 595 × 842.
How big is A3 compared with A4?
A3 is exactly twice the area of A4: 297 × 420 mm, two A4 sheets side by side.
What is the difference between ISO B5 and JIS B5?
ISO B5 is 176 × 250 mm; the Japanese JIS B5 is 182 × 257 mm. Notebooks sold in Japan and Korea as B5 usually use the JIS size.
Which envelope fits an A4 sheet?
C4 holds A4 flat, C5 holds it folded once and DL holds it folded in thirds.