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Paper Size Converter

Everyday

Compare paper sizes — A0 to A8, Letter, Legal, Tabloid, and more — in millimetres, centimetres, and inches. Find the right paper size instantly.

Reviewed by the thecalcu.com team · Last updated July 16, 2026

Millimetres (mm)
210 × 297 mm
Centimetres (cm)
21.0 × 29.7 cm
Inches (in)
8.27 × 11.69 in

All Paper Sizes

What is a Paper Size?

A Paper Size Converter shows the exact dimensions of standard paper sizes, the ISO 216 A-series used throughout most of the world, and the US sizes (Letter, Legal, Tabloid, Executive) used in North America, in millimetres, centimetres, and inches. Paper sizing is one of those details that rarely matters until it does: a document designed for A4 can print awkwardly on a Letter-size printer, and print shops, designers, and developers regularly need to know exact dimensions when setting up a layout.

This converter lets you pick any standard size and instantly see its dimensions across all three common units, alongside a full reference table for comparing every size at a glance. It pairs well with the Length Converter for general unit conversion and the Typography Unit Converter for print and design measurements.

Why Use a Paper Size Converter?

Designers, developers, and print shops regularly need exact paper dimensions, to set up a print template, configure a PDF export, or simply answer "how big is A3 compared to Letter?" without searching through a static reference chart. Because A-series and US sizes use entirely different base units (A-series is defined in millimetres, US sizes in inches), converting between them by hand is error-prone.

This converter solves that by giving instant, accurate dimensions for any standard size in all three units side by side. A developer setting print CSS for a web app, a designer preparing artwork for an international print run, or a student figuring out why their A4 essay printed oddly on a US printer can all get the exact numbers they need immediately, similar to how the Image Resolution Converter helps with digital sizing decisions.

Who Should Use This Converter?

  • Designers and print professionals setting up layouts that need to work across both ISO and US paper standards.
  • Developers configuring print stylesheets or PDF generation who need exact paper dimensions in CSS-friendly units.
  • Students and office workers troubleshooting print formatting issues between A4 and Letter-size documents.
  • International businesses preparing documents that need to print correctly regardless of the recipient's regional paper standard.
  • Architects and engineers working with the A-series sizes (A0–A3) commonly used for drawings and technical plans.

What Insights Does the Paper Size Converter Give You?

Selecting any paper size gives you its exact dimensions across the three units people most commonly need:

  • Millimetres (mm), the native unit for the ISO 216 A-series, and the most precise reference for print production.
  • Centimetres (cm), a more everyday-friendly version of the same metric measurement.
  • Inches (in), the unit US paper sizes are defined in, and the most useful reference for North American printing and design software.

The full reference table below the main result lets you compare every standard size at once, making it easy to spot, for example, that A3 is roughly double the area of A4, or that US Legal is just a taller version of US Letter.

How to use this Paper Size calculator

  1. Select a paper size from the Paper Size dropdown, choose from A0–A8 or the standard US sizes.
  2. Read the dimensions shown in Millimetres, the primary result.
  3. Check the Centimetres and Inches cards for the same dimensions in other units.
  4. Scroll the All Paper Sizes reference table to compare your selected size against every other standard size.
  5. Click any size in the reference table to instantly switch the main result to that size.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Each paper size in this converter is defined by fixed, standardised width and height values rather than a single conversion formula, ISO 216 sizes are defined directly in millimetres, and US sizes are defined directly in inches, then converted using:

Millimetres = Inches × 25.4

The ISO 216 A-series additionally follows a fixed aspect ratio of 1:√2, meaning each size is exactly half the area of the size above it:

A(n+1) width = A(n) height ÷ 2, A(n+1) height = A(n) width

Worked example: A4 (210 × 297 mm) converts to inches as:
- Width: 210 ÷ 25.4 ≈ 8.27 in
- Height: 297 ÷ 25.4 ≈ 11.69 in

Frequently Asked Questions

What is the difference between A4 and US Letter paper?
A4 measures 210 × 297 mm (8.27 × 11.69 inches), while US Letter measures 215.9 × 279.4 mm (8.5 × 11 inches), A4 is slightly narrower and noticeably taller than Letter. This difference is why documents formatted for A4 sometimes don't print cleanly on Letter-size printers, and vice versa.
What are the dimensions of A4 paper in inches?
A4 paper measures 8.27 × 11.69 inches (210 × 297 mm). It's the standard paper size used for documents, letters, and printing throughout most of the world outside North America.
Why is A4 wider in some orientations than others?
Like all ISO 216 sizes, A4 is defined by a fixed aspect ratio of 1:√2 (roughly 1:1.414), so portrait A4 is 210 mm wide and 297 mm tall, while landscape A4 simply rotates those same dimensions. This ratio is what lets two A4 sheets combine to form one A3 sheet with no wasted space.
What is the relationship between A0, A1, A2, A3, and A4?
Each size in the A-series is exactly half the area of the size above it, achieved by folding or cutting along the longer dimension, two A4 sheets make one A3 sheet, two A3 sheets make one A2 sheet, and so on up to A0. This is why architects and engineers can scale drawings cleanly between A-series sizes without distortion.
What paper size is used for legal documents in the US?
US Legal size (215.9 × 355.6 mm, or 8.5 × 14 inches) is commonly used for legal documents, contracts, and some government forms in the United States. It's the same width as Letter but about 3 inches taller.
What size is Tabloid or Ledger paper?
Tabloid (also called Ledger in landscape orientation) measures 279.4 × 431.8 mm (11 × 17 inches), exactly twice the area of US Letter, similar to how A3 relates to A4. It's commonly used for newspapers, posters, and spreadsheets needing extra width.
Can I print an A4 document on Letter paper without resizing?
You can, but since A4 is taller and narrower than Letter, the content may be cropped at the bottom or have extra blank margin, depending on your printer's scaling settings. Most printers offer a 'fit to page' or 'scale to fit' option that adjusts the content to avoid cropping.
What is US Executive paper size used for?
US Executive size (184.15 × 266.7 mm, or 7.25 × 10.5 inches) is a smaller format sometimes used for personal stationery, resumes, or executive correspondence. It's noticeably smaller than both Letter and A4.
Why does Europe use A4 while the US uses Letter?
The ISO 216 standard (which defines A4 and the rest of the A-series) was adopted internationally based on a mathematically consistent ratio, while the US continued using paper sizes that predate the ISO standard, based on older imperial paper-making conventions. Both systems remain in parallel use today depending on region.
What size is A5, and what is it commonly used for?
A5 measures 148 × 210 mm (5.83 × 8.27 inches), exactly half the size of A4. It's commonly used for notebooks, flyers, postcards, and booklets.
Also known as
A4 to letter sizepaper size chartISO paper sizesA4 dimensions in inchesUS letter size in mmA4 A5 size converterletter size to A4paper dimensions converterenvelope size converter