Guides/Resize in cm/inches

Resize image in cm or inches (convert to pixels)

Start with the physical width and height you need, calculate the pixels required at your chosen print resolution, then resize locally. Set the physical size again when printing; pixel dimensions alone do not lock it.

Print size calculator

Convert both dimensions using your chosen print resolution. No image or upload is needed.

PPI means image pixels per printed inch. Print briefs often call this “DPI”; printer dots per inch describe a different device setting.

1,200 × 1,800 px

Pixel export: 1,200 × 1,800 px. At 300 PPI, this is approximately 10.16 × 15.24 cm. Pixel output is rounded to whole pixels.

Resize to 1,200 × 1,800 px →

The resizer opens with these exact pixel dimensions and Pad mode to preserve the whole image; padding may be added if its aspect ratio differs. Neither this calculator nor the resizer writes your chosen PPI into file metadata. Set the intended physical size in your print dialog and check its scaling preview.

Resize image online
Conversion formulas
  • pixels = physical size × PPI (when physical size is in inches)
  • pixels = cm ÷ 2.54 × PPI
  • pixels = mm ÷ 25.4 × PPI
  • inches = pixels ÷ PPI
  • cm to inches: cm ÷ 2.54
  • mm to inches: mm ÷ 25.4
Pick the requested image PPI
  • Ask your print service for its image-resolution requirement.
  • 300 PPI is a common starting point for close-viewed photo prints.
  • A larger print at the same PPI needs more pixels; enlarging a small original does not recover missing detail.
PPI counts image pixels per printed inch. DPI counts printer dots; image briefs sometimes use “DPI” for PPI.
From a print specification to an export
  1. Enter the physical width, height, and requested PPI. Select cm, mm, or inches.
  2. Open the resulting whole-pixel dimensions in the resizer. Pad preserves the full image and may add margins; Crop fills the frame and can remove edges. Review the preview before exporting.
  3. In the printing app, set the intended physical width and height. Check scaling, paper size, and margins. Automatic “Fit to page” can change your requested size.

Worked examples at 300 PPI

  • 10 × 15 cm: 10 ÷ 2.54 × 300 ≈ 1181 px, and 15 ÷ 2.54 × 300 ≈ 1772 px. Export 1181 × 1772 px. Whole-pixel rounding gives approximately 9.999 × 15.003 cm at 300 PPI.
  • 4 × 6 inches: 4 × 300 = 1200 px and 6 × 300 = 1800 px. This is exactly 10.16 × 15.24 cm, slightly larger than 10 × 15 cm.
  • 35 × 45 mm: 35 ÷ 25.4 × 300 ≈ 413 px and 45 ÷ 25.4 × 300 ≈ 531 px. This is only a dimension calculation; official ID photos have separate framing, background, and acceptance requirements.
  • A3, 29.7 × 42 cm: 3508 × 4961 px after rounding. The height exceeds this resizer’s 4096 px limit, so the calculator keeps the result and disables the handoff. Use an editor that supports the required canvas.

Will the exported file say “300 DPI”?

The calculator uses PPI for the math. PixelProof’s resizer exports the chosen pixel dimensions, but it does not write your chosen PPI into the file’s resolution metadata. A printing app may read a different default resolution. Set the intended physical size in its print dialog, or use an editor with resolution-metadata controls if your print service explicitly requires that tag.

A file-size limit such as 200 KB is a separate requirement: compression, image detail, and file format affect file weight. There is no fixed KB-to-cm conversion.

Sources

Each source applies only to the claim described beside its link.

  • Adobe: Printed image resolution — Explains PPI, the relationship between pixel dimensions and physical print size, and why changing resolution without resampling does not add pixels.
    Source checked:
  • Adobe: Resolution specs for printing images — Supports 300 PPI as a common starting point for close-viewed prints and explains why viewing distance affects the resolution needed.
    Source checked:
Next steps for your print target
Single image
Review the crop or padding →

Enter the calculated pixel width and height in the resizer. Use the preview to decide whether to crop edges or preserve the image with padding.

Existing photo
Check how large your source can print →

Start with the original pixel dimensions and compare its print size at different PPI values before deciding whether to resize.

Multiple images
Prepare several photos at the same size →

Set the calculated pixel dimensions once for the batch, then review each result. Different source aspect ratios may need different crops.

Upload limit
Reduce file weight after resizing →

Use this when the print service also limits KB or MB. Inspect compression quality and confirm the output dimensions still meet your print target.

FAQ

How do I convert cm or inches to pixels?

Pixels = inches × PPI, or cm ÷ 2.54 × PPI. Calculate width and height separately and round the output to whole pixels. Quick tip: Choose Print size → pixels and use the image PPI requested by your print service, sometimes called DPI in its brief. Common mistake: Treating centimeters as a fixed pixel count without a resolution.

Will the exported file contain my chosen PPI?

No. The calculator uses PPI for conversion, and the resizer changes pixel dimensions without writing your chosen PPI into resolution metadata. Quick tip: Set the intended physical size in your print dialog. If a service requires a metadata value, use an editor with resolution-metadata controls. Common mistake: Assuming a 300 PPI calculation locks the print size or that Fit to page preserves it.

Can I resize by mm?

Yes. Select millimeters in the calculator. Pixels = mm ÷ 25.4 × PPI. Quick tip: The resizer link is available only when both rounded dimensions are between 16 and 4096 px. Larger results stay visible without automatic scaling. Common mistake: Shrinking an out-of-range pixel result without accounting for its changed physical size at the chosen PPI.