A4 size in pixels at 72, 150 and 300 dpi

The A4 size in pixels is 2480×3508 at 300 dpi, which is the number to use for anything that will be printed. At 150 dpi it is 1240×1754, and at 72 dpi it is 595×842. The paper itself never changes: A4 is always 210×297 mm. Only the density changes, and with it the number of pixels needed to fill the sheet without blur.

A4 pixel dimensions at every common dpi

If you only remember one line, remember 2480×3508. It is the size printers expect, it is what most design tools mean by "A4 for print", and it scales down cleanly to anything smaller. In the US and Canada the everyday sheet is US Letter, 2550×3300 at 300 dpi.

How to work out A4 in pixels yourself

Pixels are inches multiplied by dots per inch. A4 is defined in millimetres, so there is one conversion first: divide by 25.4 to get inches. The same three steps work for any paper size, which is handy when a printer sends an odd format.

1. 1

   Convert millimetres to inches

   210 ÷ 25.4 = 8.27 inches wide. 297 ÷ 25.4 = 11.69 inches tall.

2. 2

   Multiply by the dpi you need

   8.27 × 300 = 2480. 11.69 × 300 = 3508. Use the unrounded inch figures for accuracy.

3. 3

   Round to whole pixels

   Round to the nearest pixel. A one pixel difference is invisible on paper, so nobody will notice 3507 or 3508.

4. 4

   Add bleed if the colour runs to the edge

   Add 3 mm to every side before converting: 216×303 mm becomes 2551×3579 pixels at 300 dpi.

// Paper size in millimetres to pixels at a given dpi
const toPx = (mm, dpi) => Math.round((mm / 25.4) * dpi)

const a4 = { w: 210, h: 297 }
console.log(toPx(a4.w, 300), toPx(a4.h, 300)) // 2480 3508

// With 3 mm bleed on every side
console.log(toPx(a4.w + 6, 300), toPx(a4.h + 6, 300)) // 2551 3579

The difference between dpi and ppi trips people up, but for this sum they behave the same: both describe how many pixels land in an inch of paper. DPI vs PPI untangles the two properly.

Which A4 resolution should you use

For print, use 300 dpi. A4 is held at reading distance, about the length of a forearm, and at that distance 300 pixels per inch is where edges stop looking soft. Below roughly 200 dpi, small type and thin lines start to blur. Going above 300 rarely helps unless the page is fine linework or tiny technical text.

For a document that will only ever live on screen, such as a PDF guide people scroll on a laptop, 150 dpi is plenty and keeps the file light. The 72 dpi figure is less a resolution than a coincidence: PDF measures pages in points, 72 to the inch, so an A4 PDF page reports itself as 595×842 whatever is inside it.

A4 next to the other A sizes

Every A size is half the one before it, folded across the long side, and every one keeps the same 1:√2 shape, about 1:1.414. That is why an A4 design scales to A3 or A5 without cropping a thing: only the pixel count changes.

Designing an A4 page that prints well

Pixel size is only the first decision. A good A4 page also needs a safe margin, type that reads at arm's length and colour that survives the trip from screen to paper. The portrait A4 poster below holds every word well inside the trim.

• Margins: keep text at least 5 mm, about 60 pixels at 300 dpi, inside the trim. 10 mm looks calmer.
• Body type: 9 to 12 point reads comfortably on A4. At 300 dpi, 10 point text is roughly 42 pixels tall.
• Headlines: on a poster seen from across a room, go far larger than feels natural on screen.
• Colour: bright screen colours often print duller. RGB vs CMYK explains why and what to do.

Gradients deserve particular care on paper, because smooth blends are where banding shows. Printing gradients covers the fix, and print ready PDF covers the file you hand over. In Gradiently, A4 is one of the built in print sizes at 300 dpi, and Pro exports a print PDF with bleed and crop marks, so you design at the trim size and the export adds the rest.