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Paper Size Converter

Converters · Added

A4 is 210 × 297 mm, 8.27 × 11.69 inches, 595 × 842 points and 2,480 × 3,508 pixels — but only that last one at 300 DPI, and at 72 DPI it is something else entirely. This converter gives every standard sheet in all five, states which figure the standard actually defines and which is converted, and will find the nearest standard size for a measurement of your own.

Start from

The everyday series. A4 is the office default across most of the world, and each size is exactly half of the one above it.

Orientation
DPI

A pixel has no physical size until a resolution is chosen

Result

A4

210.0 × 297.0 mm

8.268 × 11.693 inches

Pixels at 300 DPI
2,480 × 3,508

8.70 megapixels

Points (PDF, design tools)
595.3 × 841.9

72 points to the inch

Aspect ratio
1.414

1 : √2 — the ISO ratio, so halving it gives the same shape again

UnitWidthHeight
Millimetres210.00297.00
Centimetres21.00029.700
Inches8.267711.6929
Points595.3841.9
Pixels2,4803,508
Area
0.0624 m² · 96.67 in²
Defined in
Millimetres — the millimetre figures are the standard, the inches are converted

The default office sheet everywhere except North America.

The pixel column depends entirely on the resolution above. A file that is 2,480 × 3,508 pixels is A4 at 300 DPI and A2 at 75 DPI — the pixels have not changed, only the size they are asked to print at. Send print work at the resolution the printer specified, which for commercial work is usually 300.

How to use the paper size converter

  1. 1Pick a series — ISO A for everyday paper, B for posters and books, C for envelopes, or the North American sizes.
  2. 2Choose the size and the orientation.
  3. 3Set the resolution for the pixel column. Use 300 for print, 96 for the CSS reference pixel, or type your own.
  4. 4Read the table for millimetres, centimetres, inches, points and pixels.
  5. 5To go the other way, switch to a custom measurement, enter a width and height in any unit, and the nearest standard size is named underneath with how far off it is.

Examples

A4 for a print file

Input
A4, portrait, 300 DPI
Result
210 × 297 mm · 8.268 × 11.693 in · 595.28 × 841.89 pt · 2480 × 3508 px

The point figures are what a PDF stores internally: 595 × 842 is the number you will see in any PDF inspector for an A4 page.

Which envelope takes an A4 sheet

Input
C4 from the envelope series
Result
229 × 324 mm — an A4 sheet plus clearance on all four sides

C5 takes A4 folded once and C6 takes it folded twice. That relationship is why the C series exists as a separate series at all.

Identifying an unlabelled sheet

Input
Custom: 8.5 × 11 inches
Result
Closest standard: Letter — an exact match

Enter measurements in millimetres, inches or even pixels at a stated DPI, and the closest standard is reported with the percentage difference.

About the paper size converter

One ratio, one series, one square metre

The ISO A series is one of the more elegant standards in daily use, and all of it follows from two decisions. The ratio of long side to short is the square root of two, and A0 has an area of exactly one square metre. Everything else is arithmetic: A1 is A0 halved across the long side, A2 is A1 halved, and so on down to A10.

The choice of ratio is what makes it work. 1:√2 is the only proportion preserved under halving, so every size in the series is the same shape. Enlarging A4 to A3 is a scale factor of √2, about 141%, and reducing A3 to A4 is about 71% — the two numbers printed on every office photocopier. Nothing needs re-laying out, and no content is lost to a changing aspect ratio.

The area rule gives the series its other convenience: paper weight in grams per square metre translates directly into sheet weight. An A4 sheet is one sixteenth of a square metre, so 80 gsm paper weighs exactly 5 g a sheet — which is how postal weight limits and sheet counts are worked out without a scale.

The B series fills the gaps, sitting geometrically between consecutive A sizes for posters, books and anything an A size is slightly too small for. The C series is sized for envelopes, and its relationship to the others is the practical one most people meet: a C4 envelope takes a flat A4 sheet, C5 takes it folded once, C6 folded twice.

Pixels, points and the resolution question

The most common request behind this tool is a pixel dimension, and it is the one that needs a caveat. Pixels are a count, not a size. A 2,480 × 3,508 pixel image is A4 at 300 DPI, A5 at 600 DPI and A2 at 150 — the file has not changed at all, only the physical size it is being asked to occupy.

This is why print work is specified as an image size and a resolution together. Commercial printing generally wants 300 DPI, which is where the detail stops being resolvable at reading distance; large-format work viewed from further away is routinely produced at 150 or less, because nobody stands six inches from a billboard. Sending a 96 DPI screen graphic to be printed at A3 is the usual way to discover this, and the result is visibly soft rather than obviously wrong.

Points sit between the two worlds. At 72 to the inch they were the original PostScript unit and they remain the internal geometry of PDF, which is why an A4 PDF page reports as 595 × 842 in every tool that shows you the raw numbers. That number is resolution-independent, unlike the pixel figures, which is precisely the point of a vector format.

Frequently asked questions

Why does A4 halve so neatly into A5?
Because the whole series is built on an aspect ratio of one to the square root of two, which is the only ratio that survives being halved. Fold a 1:√2 sheet across its long side and the two halves have exactly the same proportions as the original. A0 is defined as one square metre at that ratio, and every smaller size is the half of the one above — so a document laid out for A4 scales onto A3 or A5 without any change of proportion, and photocopiers can offer a single button for it.
How many pixels is A4?
That depends entirely on the resolution, and the question has no answer without one. A pixel has no physical size — it acquires one only when you decide how many of them go in an inch. A4 is 2,480 × 3,508 pixels at 300 DPI, 1,240 × 1,754 at 150, and 794 × 1,123 at the CSS reference of 96. A file described as being A4 without a stated DPI is not fully specified, which is why print shops always name one.
Why are the ISO figures whole millimetres rather than exact?
Because ISO 216 rounds each dimension down to a whole millimetre at every halving. Computing the series by repeated division gives A4 as 210.224 × 297.302, and rounding that happens to land on the standard's 210 × 297 — but further down the series the luck runs out, and A7 comes out 74.25 × 105.11 against the published 74 × 105. The figures on this page are the published ones, not derived, for exactly that reason.
What is the difference between Letter and A4?
Letter is 8.5 × 11 inches, about 216 × 279 mm. Against A4 it is roughly 6 mm wider and 18 mm shorter, and their aspect ratios differ — 1.294 against 1.414 — which is why neither scales onto the other without either margins changing or content being clipped. Letter also belongs to no series: unlike the ISO sizes it has no halving relationship to anything, which is why the North American sizes need their own separate names rather than a numbered sequence.
What are points, and why does my design tool use them?
A point is one seventy-second of an inch, inherited from typography and carried into PostScript and then PDF. Page geometry inside a PDF is measured in points, so an A4 page is stored as 595.28 × 841.89 regardless of what units the application shows you. Type sizes use the same unit, which is why a 12 pt line of text is a sixth of an inch tall.

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