A4 at 300 DPI: 2480 by 3508 pixels
2480 by 3508 pixels is A4 at 300 dots per inch. The A series is built on a 1 to root two ratio, which this rounds to 620:877, and the canvas comes to 8.7 megapixels.
At a glance
- Dimensions
- 2480 × 3508 pixels
- Simplified aspect ratio
- 620:877
- Decimal ratio
- 1:1.41
- Megapixels
- 8.70 MP (8,699,840 pixels)
- CSS aspect-ratio
- aspect-ratio: 620 / 877;
- Preset category
- Where it is used
- Print ready A4 documents and posters at photographic quality
In detail
The conversion is straightforward arithmetic. A4 is 210 by 297 millimetres, which is 8.268 by 11.693 inches, and multiplying by 300 dots per inch gives 2480.3 by 3507.9. Rounding to whole pixels produces the familiar 2480 by 3508, and the rounding is the reason the ratio comes out as 620:877 rather than as an exact irrational number.
The A series is defined by that irrational number. Every A size has a height to width ratio of the square root of two, about 1.41421, which is the only ratio with the property that halving the long side produces the same shape again. That is why A5 is exactly half an A4 and why enlarging A4 to A3 needs no crop.
Three hundred dots per inch is the conventional target for photographic print quality, and it is a choice rather than a law. Large format work viewed from a distance is routinely produced at 150, and fine art reproduction sometimes goes higher. The pixel dimensions scale linearly with the number you pick, so halving the resolution halves both dimensions.
Anything printing to the edge of the sheet needs bleed, extra artwork beyond the trim line that gets cut away. Printers commonly ask for three millimetres on each side, which at 300 dots per inch is about 35 pixels, so a full bleed A4 document is set up nearer 2551 by 3579 and trimmed back.
Examples
210 mm / 25.4 = 8.268 in -> * 300 = 2480 px
297 mm / 25.4 = 11.693 in -> * 300 = 3508 px
at 150 dpi: 1240 x 1754
at 600 dpi: 4961 x 70163508 / 2480 = 1.41452
Math.SQRT2 = 1.41421
// A5 is 1754 x 2480: the long side halved, same shapeThings that catch people out
- Pixel dimensions mean nothing without a resolution. 2480 by 3508 is A4 at 300 DPI and a very large poster at 72.
- Artwork that runs to the edge needs bleed, or the trim leaves a white hairline where the cut missed.
- A4 and US Letter are different shapes, not just different sizes. A document laid out for one has wrong margins on the other.
Try it: Aspect Ratio Calculator
Enter a width and a height, or a ratio and one dimension, and it solves the missing one, simplifies the ratio, counts the megapixels and gives you a copyable CSS value.
Aspect Ratio Calculator
LOCAL · Browser-OnlyCalculate and convert aspect ratios for images, videos, and screens
1920 x 1080px · 16:9 · 1.7778:1
Common Aspect Ratios Reference
| Ratio | Decimal | Common Use |
|---|---|---|
| 16:9 | 1.778 | Widescreen TV, YouTube, monitors |
| 4:3 | 1.333 | Classic TV, iPad, presentations |
| 1:1 | 1.000 | Instagram square, profile pictures |
| 21:9 | 2.333 | Ultrawide monitors, cinema |
| 9:16 | 0.563 | Phone vertical, TikTok, Reels |
| 3:2 | 1.500 | 35mm photography, MacBook |
| 2:3 | 0.667 | Portrait photography, posters |
| 5:4 | 1.250 | Large format photography, older monitors |
| 32:9 | 3.556 | Super ultrawide monitors |
| 2.39:1 | 2.390 | Anamorphic cinema, widescreen films |
Related Image and canvas sizes
All image and canvas sizes →US Letter at 300 DPI: 2550 by 3300 pixels
How 8.5 by 11 inches becomes exactly 2550 by 3300 pixels at 300 DPI, the 17:22 ratio it reduces to, and why it does not interchange with A4.
DPI versus pixel dimensions
Why a raster file only stores pixels, what the DPI number in its metadata does and does not change, and how to work out a print size from a pixel count.
Business card at 300 DPI: 1050 by 600 pixels
The 1050 by 600 pixel card canvas, the 3.5 by 2 inch physical size behind it, the 7:4 ratio, and the bleed and safe margins a printer expects.
OG image size: 1200 by 630
The 1200 by 630 open graph image, why it became the default sharing size, the markup that nominates it, and the rules that make it actually appear.
Favicon at 512 by 512
The 512 by 512 icon canvas, why a favicon is a set of sizes rather than one file, and exactly which outputs the favicon generator here produces.
iOS app icon size: 1024 by 1024
The 1024 by 1024 app icon master, why the corners should be left square, why transparency is a problem, and how the smaller sizes derive from it.
Tools for this
- Aspect Ratio Calculator Free online aspect ratio calculator - calculate and convert aspect ratios for images, videos, and screens
- Image Resizer Free online image resizer - resize images to exact dimensions, percentage, or common presets