Why a Letter printable shrinks on A4 paper

Letter and A4 do not match

US Letter is 8.5 × 11 inches, or 215.9 × 279.4 mm. A4 is 210 × 297 mm. In portrait orientation, A4 is narrower and taller, so a full Letter page has to shrink to fit inside it. That changes printed rulers, labels and cut lines.

These figures assume an ideal full sheet with no printer margins. A printer’s non-printable edges can reduce the available area and force more shrinking. The tool calculates the geometry from the dimensions entered; it does not read PDF page settings or control a printer.

What the fit setting does

Start with a 2550 × 3300 pixel image placed as a Letter page at 300 PPI. In the tool, enter those source dimensions, choose Portrait and Fit, set bleed to zero, then compare US Letter with A4. Pixels alone do not set a physical page size; 300 PPI is a stated baseline for this example.

A4 width limits the ideal fit: 210 ÷ 215.9 = 97.2673% of the Letter size. The artwork becomes 210 × 271.765 mm. Its effective density rises from 300 to about 308.43 PPI because the same pixels occupy less physical space. No detail has been added.

2550 × 3300 px at 300 PPI → 8.5 × 11 in Letter. Fitted to ideal A4: 210 × 271.765 mm at 97.2673% scale.

Measure a mark, not the page preview

A one-inch calibration mark is 25.4 mm at its intended Letter size. After a 97.2673% fit, it is 25.4 × (210 ÷ 215.9) = 24.7059 mm, or about 0.973 inches. A page can look complete in preview while its measurements are wrong.

An ideal A4 sheet has about 25.235 mm of unused height. A centered placement divides it between the top and bottom. Print-dialog margins and positioning can move those borders.

• Select the paper actually loaded in the printer.
• For measurements, use a document made for that paper and select actual size or 100%.
• Print one test copy and measure a known mark before cutting or printing a batch.
• A wider document printed at its original size can be clipped. Check the edges in the preview.
• For a calibration square, measure both directions. Correct paper or scaling settings before printing a batch; the calculator cannot confirm the printer preserved the chosen scale.