# Paper Size Reference

Free paper size reference tool. Look up dimensions for A-series, B-series, US Letter, Legal, Tabloid, and more in mm, cm, or inches.

## What this calculates

Look up dimensions for any standard paper size in millimeters, centimeters, or inches. Covers ISO A-series and B-series (international), US Letter, Legal, Tabloid, and other North American sizes.

## Inputs

- **Paper Size** — options: A0, A1, A2, A3, A4, A5, A6, A7, B0 (ISO), B1 (ISO), B2 (ISO), B3 (ISO), B4 (ISO), B5 (ISO), US Letter, US Legal, US Tabloid (11x17), US Executive, US Half Letter (Statement)
- **Display Units** — options: Millimeters (mm), Centimeters (cm), Inches (in)

## Outputs

- **Dimensions (W x H)** — formatted as text — Width and height of the paper size.
- **Dimensions (mm)** — formatted as text — Width and height in millimeters.
- **Dimensions (inches)** — formatted as text — Width and height in inches.
- **Area** — formatted as text — Paper area
- **Aspect Ratio** — formatted as text — The aspect ratio of the paper.
- **Standard** — formatted as text — Which standard this paper size belongs to.

## Details

Paper sizes follow different standards internationally. Most of the world uses the ISO 216 standard (A-series), while the US and Canada primarily use Letter and Legal sizes.

ISO A-Series (International)

The A-series is based on two principles:

- All sizes have an aspect ratio of 1:√2 (≈1:1.4142)

- A0 has an area of exactly 1 square meter

Each subsequent size is half the previous one: A1 = A0 folded in half, A2 = A1 folded in half, etc.

Most Common Sizes

- A4 (210 × 297 mm): Standard international paper, similar to US Letter

- US Letter (8.5 × 11 in / 215.9 × 279.4 mm): Standard in US/Canada

- A3 (297 × 420 mm): Double A4, used for larger documents

- US Legal (8.5 × 14 in): Used for legal documents in the US

- Tabloid/Ledger (11 × 17 in): Double Letter size

A4 vs. US Letter

A4 is narrower but taller than US Letter. A4: 210 × 297 mm. Letter: 215.9 × 279.4 mm. This can cause formatting issues when printing documents designed for one size on the other.

## Frequently Asked Questions

**Q: What is the difference between A4 and US Letter?**

A: A4 (210 × 297 mm) is narrower and taller than US Letter (215.9 × 279.4 mm / 8.5 × 11 in). A4 is 5.9 mm narrower but 17.6 mm taller. Most of the world uses A4, while the US and Canada use Letter size. Set your printer to the correct size to avoid scaling issues.

**Q: Why does the A-series use a 1:√2 ratio?**

A: The 1:√2 ratio is mathematically special because folding a sheet in half produces a new sheet with the same proportions. This means A4 has the same shape as A3, A5, etc., making it easy to scale documents up or down without distortion or margin changes.

**Q: What is A0 paper used for?**

A: A0 (841 × 1189 mm, about 33 × 47 inches) has an area of 1 square meter and is used for large technical drawings, architectural plans, and posters. It is the largest standard A-series size. Professional wide-format plotters can print A0 and larger.

**Q: What paper size should I use for printing envelopes?**

A: ISO C-series envelopes are designed to fit A-series paper: C4 fits A4 unfolded, C5 fits A4 folded in half, C6 fits A4 folded in quarters. US standard envelopes: #10 (4.125 × 9.5 in) fits Letter paper folded in thirds.

---

Source: https://vastcalc.com/calculators/conversion/paper-size-reference
Category: Conversion
Last updated: 2026-04-21