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Convert preset C-series millimeter dimensions into pixel estimates using a selected DPI.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
This converter estimates pixel width and height from a selected C-series preset and a dots-per-inch (DPI) value. Its preset list runs from C0 through C10, with each entry supplying a width and height in millimeters. The result is two whole-number pixel dimensions; the tool does not create or resize an image.
DPI is the number of image pixels assigned to each inch of intended physical length for this calculation. Since one inch is exactly 25.4 mm, each side is converted independently:
For example, the preset C4 dimensions are 229 × 324 mm. At 300 DPI, that gives round((229 ÷ 25.4) × 300) = 2705 px and round((324 ÷ 25.4) × 300) = 3827 px. Rounding means the displayed integer can differ slightly from an ideal fractional-pixel calculation.
The C0–C10 names describe the choices available here; they should not be read as a claim that every listed size is a currently standardized envelope size. ISO 269:1985 concerned correspondence envelopes and is marked withdrawn in the ISO catalog. The conversion uses the page’s preset dimensions as inputs and does not certify a paper specification.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Choose a name from C0 to C10. Check the millimeter width and height shown in the size list against the specification you intend to use.
Adjust the slider or enter a value. Quick selections include 72, 96, 150, 300, and 600 DPI; the slider covers 72 to 600. Use the value requested for your output workflow.
Read width and height separately, then copy each number into your design document’s canvas settings. The displayed orientation follows the preset dimensions; swap the sides in your design app if you need a landscape canvas.
Use cases
See how the tool fits into real work and everyday tasks.
A designer preparing artwork associated with a C4 envelope can select C4 and the production DPI, then transfer the resulting canvas width and height into a separate design application.
A production coordinator can convert a supplied millimeter size at the requested DPI and compare both pixel sides with a brief before sending files to a printer.
For a mockup that needs a particular pixel canvas, select the relevant preset and a chosen resolution value. Keep the intended physical size and DPI with the result so others can reproduce the estimate.
Q&A
Find concise answers to common questions and confusing cases.
Using this page’s 229 × 324 mm preset, the result is 2705 × 3827 px after rounding each side to a whole pixel.
No. The selected millimeter dimensions stay the same; a higher DPI assigns more pixels to each inch, so the calculated pixel width and height increase.
The math uses a numeric pixels-per-inch rate. Enter the rate appropriate to your task; the displayed control is labeled DPI, and the result is only a dimension estimate based on that number.
Notes
Review scope, result limitations, and important precautions before use.
The output is a mathematical estimate from preset millimeter dimensions and the selected DPI. It does not add bleed, trim marks, or image detail, and it does not resize an existing file or set its print-resolution metadata. A pixel canvas alone cannot guarantee print quality or a fit with a particular envelope or printer. Confirm the actual finished size, orientation, bleed, and resolution with the printer or project specification.
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