Poster Size: Convert Inches, Millimeters, and Pixels at a Chosen PPI

Calculate the raster pixel dimensions for a poster from its physical width, height and intended pixels per inch. Choose a common size or enter a custom size, then check your image dimensions against the printer or conference requirements.

Use the Poster Size Calculator to convert dimensions at your chosen PPI. The calculations run locally and require no credits.

Original AI-generated poster size calculator reference commissioned by AcaDraw. Illustrative teaching example; review labels and relationships before use.

Physical size comes before resolution

Start with the size requested by the venue: for example, a 36 × 48 inch poster. Then choose the raster resolution required by the printer. At 150 PPI, that size needs 5,400 × 7,200 pixels; at 300 PPI it needs 10,800 × 14,400 pixels.

Those are target dimensions, not a promise that an image will contain that much useful detail. A small source enlarged to the target can remain blurry. For text and linework, use vector or editable text where possible.

Metric conversion and rounding

One inch is exactly 25.4 mm. To convert a width in millimeters to pixels, divide by 25.4 and multiply by the selected PPI. For centimeters, multiply by ten first. The calculator rounds upward to whole pixels so the result is not below the chosen target.

For A1 at 150 PPI, 594 mm becomes 3,508 pixels after upward rounding, and 841 mm becomes 4,967 pixels. A0 uses 841 × 1189 mm. Landscape orientation swaps width and height without changing the physical area.

PPI, DPI and the final file

PPI describes image pixels per printed inch. Printer DPI describes the device’s dot placement. Their numbers can differ; do not copy one specification into the other without checking what the printer requests.

Use the poster size calculator for dimensions, then check fonts, linework, margins, color requirements and export format in the layout editor. Changing the resolution tag alone cannot add missing detail. If the source ratio differs from the poster ratio, crop or reposition rather than stretching the illustration.

Poster Size Calculator reference key

From dimensions to a poster brief

Checks before sharing

Metadata used as upscaling. Changing a PPI tag without adding pixels cannot recover detail.

Blank or zero dimensions. Use positive finite dimensions and a sensible positive resolution.

Aspect ratio ignored. Stretching a source image to a different poster ratio can distort the content.

Common questions

How do I convert poster inches to pixels?

Multiply each dimension in inches by the target PPI. This calculator rounds up to whole pixels.

Is A0 twice the width of A1?

No. A0 is 841 × 1189 mm and A1 is 594 × 841 mm; their areas differ by about a factor of two.

Does choosing 300 PPI improve a small source image?

No. It calculates the target dimensions. Existing artwork needs enough real detail at that size.

Is this calculator free?

The local size conversion works without an account or credits. Generating a poster concept is a separate account-and-credit workflow.

Sources and editorial notes

• Adobe: A0 Paper Format
• Adobe: A1 Paper Format

Prepared by the AcaDraw product team on November 10, 2026. The illustration is an original AI-generated teaching example. Reference links support the concepts; they do not imply endorsement or independent review of this article.