Applies to: Finished sheet dimensions and mathematical fit examples. Actual printer margins can require additional reduction.
A4 is 210 × 297 mm (8.27 × 11.69 in). US Letter is 8.5 × 11 in (215.9 × 279.4 mm). Letter is wider; A4 is taller. Use flexible margins or provide separate versions when layout matters.
The measurements
A4 belongs to the ISO 216 A-series used in most countries. Letter is common in the United States and Canada. Their areas are similar, but their proportions differ enough to affect page breaks, forms, labels, and border designs.
A document designed with generous margins often transfers between the two. A full-page design or tightly fitted table may not.
What happens when you print one on the other
Printing A4 on Letter at Actual Size can clip content near the top or bottom because Letter is shorter. Printing Letter on A4 can clip content at the sides because A4 is narrower. Fit avoids clipping but makes the page slightly smaller.
For forms with measurement boxes, labels, or templates, scaling may make the output unusable. Provide the correct paper-size version instead.
Design documents that travel well
- Use margins of at least 0.5 inch or about 13 mm unless your printer requires more.
- Avoid positioning essential elements at the page edge.
- Keep tables flexible and check page breaks.
- State the intended paper size next to the download link.
- Export and inspect both A4 and Letter versions when serving an international audience.
Choose the right default
Use the standard expected by the person printing the document. Changing only the printer setting does not change the source document’s layout.
For a shared template, create two properly laid-out files and label them clearly rather than asking every recipient to troubleshoot scaling.
See which edge causes the mismatch
The diagram uses the same scale for both sheets. Letter extends 5.9 mm farther across, while A4 extends 17.6 mm farther down. These differences explain why neither format is a drop-in replacement for a tightly fitted page.
Calculate the full-sheet fit before hardware margins
For A4 onto Letter in portrait, compare both ratios: 215.9 ÷ 210 and 279.4 ÷ 297. The smaller is approximately 94.07%, set by height. For Letter onto A4, the limiting ratio is 210 ÷ 215.9, approximately 97.27%, set by width.
These calculations assume the whole source sheet must fit inside the whole destination sheet with no rotation. A printer with non-printable margins has a smaller destination rectangle and may require more reduction. A design whose content already sits inside generous margins may need none.
Sources and further reading
Vendor instructions and background references are linked below. Worked examples are our explanatory calculations, not vendor performance claims. Check the instructions for your current software and device.
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