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Paper Size Converter

Unit Converters

A/B/C series in mm and inches with area

Quick Answer

Paper Size Converter: A/B/C series in mm and inches with area. A0 = exactly 1 m² (841×1189mm); constant ratio 1:√2.

A series (printing)

B series (posters/books)

C series / DL (envelopes)

A4210 × 297mm
Size in inches8.27 × 11.69in
Area0.0624m²
1 A0 sheet ≈16.03A4 sheets
Aspect ratio1 : 1.414√2

How the series works

  1. 1A0 is exactly 1 m²: 841 × 1189 mm = 0.9999 m² ≈ 1 m²
  2. 2Each size halves the long edge of the previous: A1 = A0 folded (594×841), A2 = A1 folded (420×594)…
  3. 3Halving keeps the 1:√2 ratio, so two A5 sheets exactly tile one A4

Common uses

SizeTypical use
A4Documents / printing standard
A3Posters / spreadsheets / drawings
A5Notebooks / flyers
A6Postcards / pocket notes
B5Books / magazines
C5Envelope for folded A4
DLEnvelope for A4 folded in thirds
ISO 216: A0 is exactly 1 m²; each halving of the long edge gives the next size, keeping the 1:√2 ratio — so two A5 sheets equal one A4. The US uses Letter (216×279 mm) instead of A4: slightly wider and shorter, a common cause of misaligned printouts.

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How to Use

  1. Pick units: switch source and target units in the Paper Size Converter.
  2. Enter a value: results sync both ways instantly — no convert button needed.
  3. Use the reference table: common conversions are listed for instant lookup.
  4. Copy the result: copy the converted value with its unit.

Key Points

  • Paper Size Converter is a free online unit conversion tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: A/B/C series in mm and inches with area.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

ISO 216 paper sizes

A0 = exactly 1 m² (841×1189mm); constant ratio 1:√2
Halving the long edge yields the next size; A4 = 210×297mm
B series is √2× the same A number; C envelopes fit A sheets (C4 holds A4 flat)

FAQ

How do I use the Paper Size Converter?
Open the page and fill in the input fields — results update automatically. A/B/C series in mm and inches with area.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on SI conversion factors and international standards. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

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Results provided by this tool are for reference only and do not constitute professional advice.