Reference library

C9 Envelope Paper Size

C9 measures 40 x 57 mm, 4 x 5.7 cm, or 1.57 x 2.24 in. See pixel dimensions by DPI, aspect ratio, bleed setup, comparisons, and related tools.

Last checked: 2026-05-01

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At a glance

C9 is 40 x 57 mm, 4 x 5.7 cm, or 1.57 x 2.24 in. At 300 DPI, C9 is 472 x 673 px.

Last checked: 2026-05-01 Source: ISO 269:1985 Found a spec change? Send correction.

How we calculate this

Methodology and source handling

We convert physical sizes to inches, multiply by the selected DPI/PPI value, and round to whole pixels.

Methodology Editorial policy

Quick answer

Copy-ready answer

C9 is 40 x 57 mm, 4 x 5.7 cm, or 1.57 x 2.24 in. At 300 DPI, C9 is 472 x 673 px.

40 x 57 mm

Dimensions and specs

Millimeters	40 x 57 mm
Centimeters	4 x 5.7 cm
Inches	1.57 x 2.24 in
300 DPI pixels	472 x 673 px
Aspect ratio	1:1.425
Standard family	ISO C Envelope Series

Pixels

Pixel dimensions by DPI

DPI / PPI	Width	Height	Use
72 DPI	113 px	162 px	Screen or draft reference density
96 DPI	151 px	215 px	Screen or draft reference density
150 DPI	236 px	337 px	Screen or draft reference density
300 DPI	472 px	673 px	Common high-quality print setup
600 DPI	945 px	1346 px	High-resolution archival or print workflow

Formula

How to calculate this size

Pixel formulapixels = millimeters / 25.4 x PPI

40 mm x 300 PPI = 472 px wide.

Trim result472 x 673 px

Use this when the artwork stops at the finished edge.

Bleed result472 x 673 px

Add 0 mm per side before calculating pixels when artwork reaches the edge.

Common mistakes

Avoid these c9 envelope paper size problems

Mixing screen pixels with print quality

A paper size needs a PPI target before pixels mean anything for print.

Forgetting orientation

Portrait and landscape use the same dimensions, but width and height swap in the export.

Adding bleed to a paper reference

Paper pages show trim size first; add bleed only when the design prints to the edge.

Calculator

Calculate pixels and bleed

Enter any DPI to calculate the pixel dimensions for this physical size.

Compare

Compare C9 Envelope Paper Size

Open a curated comparison or send both sizes into the compare tool with a fragment URL.

compare tool C9 vs C8

C9 Envelope Paper Size: 40 x 57 mm
C8: 57 x 81 mm

50.6% smaller than C8 Envelope Paper Size. 0.0019 decimal ratio difference compare tool C9 vs C10

C9 Envelope Paper Size: 40 x 57 mm
C10: 28 x 40 mm

103.6% larger than C10 Envelope Paper Size. 0.0018 decimal ratio difference compare tool C9 vs A4

C9 Envelope Paper Size: 40 x 57 mm
A4: 210 x 297 mm

96.3% smaller than A4 Paper Size in Pixels, Millimeters, Centimeters and Inches. 0.0053 decimal ratio difference compare tool C9 vs US Letter

C9 Envelope Paper Size: 40 x 57 mm
US Letter: 215.9 x 279.4 mm

96.2% smaller than US Letter Paper Size. 0.071 decimal ratio difference

C9 belongs to the ISO C Envelope Series family. Use this reference for print setup, document layout, template sizing, pixel conversion, and comparisons with nearby paper sizes. Pixel dimensions are calculated from the physical size and selected DPI.

Workflow

Use C9 Envelope Paper Size in a finished file

Confirm the physical size

Copy the millimeter, centimeter, or inch dimensions for the selected paper standard.

Choose PPI

Use 300 PPI for most sharp print exports, or match the printer requirement.

Calculate pixels

Multiply inches by PPI, then add bleed only when artwork reaches the trimmed edge.

Related pages and tools

same series C8 paper size same series C10 paper size common alternative A4 paper size common alternative US Letter paper size comparison C9 vs C8 comparison C9 vs C10 tool DPI calculator tool Print bleed calculator tool Compare sizes tool

Same branch

Nearby pages

A4 Paper Size in Pixels, Millimeters, Centimeters and Inches A5 Paper Size Legal Paper Size US Letter Paper Size A0 Paper Size A1 Paper Size A10 Paper Size A2 Paper Size

FAQ

Common questions

What is the exact C9 size?

C9 measures 40 x 57 mm, 4 x 5.7 cm, or approximately 1.57 x 2.24 in.

What is C9 in pixels at 300 DPI?

C9 at 300 DPI is 472 x 673 px when rounded to the nearest whole pixel.

What aspect ratio is C9?

C9 has an aspect ratio of about 1:1.425 based on its 40 x 57 mm physical dimensions.

Should I add bleed to a C9 design?

Envelope print workflows vary by provider and production method. Confirm bleed, flap, and safe-area requirements with the printer or envelope template before output.

References

Sources and references

ISO 269 physical dimensions. Pixel values are calculated from millimeters / 25.4 x DPI and rounded to whole pixels.

ISO 269:1985
Used for ISO C envelope dimensions and DL envelope references.
HP paper size reference
Used as a reputable printer reference for North American office, ANSI, and envelope dimensions.
W3C CSS Values and Units Module
Used for CSS unit definitions, absolute unit relationships, and CSS px behavior.

Last checked: 2026-05-01