What's the difference between A4 and Letter size?

A4 (210 × 297mm) is the ISO 216 standard used across most of the world; Letter (215.9 × 279.4mm) is the US and Canada standard. They're a similar size but not identical, A4 is narrower and taller than Letter.

How is the pixel size calculated at a given DPI?

Pixels = (millimetres ÷ 25.4) × DPI, converting the physical dimension to inches and multiplying by the print resolution. For example, A4 at 300 DPI works out to 2480 × 3508 pixels.

Paper Size Converter

Convert standard paper sizes (A4, Letter, Legal) between mm, inches and pixels.

How this is calculated

Standard ISO 216 / ANSI paper dimensions; pixels = (mm ÷ 25.4) × DPI

Assumptions used in this calculation

Standard sizes only: Uses official ISO 216 (A-series) and ANSI/US paper dimensions. Custom, regional, or non-standard paper sizes outside these two systems are not included.

About this calculator

The paper size converter shows the dimensions of standard ISO A-series and US paper sizes in millimetres, inches and pixels at a given print resolution.

Worked example

A4 at 300 DPI

Result: 210 × 297 mm, 2480 × 3508 px

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Paper Size Converter

About this calculator

Frequently asked questions

What's the difference between A4 and Letter size?

How is the pixel size calculated at a given DPI?

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