A4 vs Letter: Size Differences and Printing Examples
A4 is 210 × 297 mm; US Letter is 215.9 × 279.4 mm. Letter is 5.9 mm wider, while A4 is 17.6 mm taller. That difference matters for printables with measured grids, full-page tables and content close to an edge.
| Sheet | Width | Height | Shape |
|---|---|---|---|
| A4 | 210 mm | 297 mm | Narrower and taller |
| Letter | 215.9 mm | 279.4 mm | Wider and shorter |
What happens to an A4 PDF on Letter?
With Actual Size, the artwork keeps its dimensions, but anything outside Letter’s height or the printer’s printable area may be cut off. With a uniform full-sheet fit, compare 215.9 ÷ 210 and 279.4 ÷ 297. Height limits the scale to 94.07%. A 50 mm square becomes about 47.04 mm. This calculation assumes the complete sheet is available; real margins can reduce the scale further.
And Letter on A4?
Width limits the full-sheet scale to 210 ÷ 215.9 = 97.27%. A 100 mm reference would become 97.27 mm. These percentages explain a possible mismatch; a ruler reading by itself cannot prove which print setting caused it.
Choose the setting by the task
- For a ruler, sewing pattern or measured grid, download the version matching your loaded paper and use Actual Size.
- For a reading copy where size is flexible, Fit can keep content inside the printable area. Check that text remains legible.
- For a layout that needs all its original dimensions on a smaller sheet, tile the PDF or use larger paper.
- Measure the printed reference. Changing the PDF filename from A4 to Letter does not resize its pages.
Which version should a printable offer?
Offer both when the design depends on exact dimensions. Keep spacing identical in millimetres and adjust the usable layout to each sheet. A Letter grid may have fewer rows than its A4 counterpart without changing the grid spacing.
Sources and method
- ISO 216:2007: the scope of the ISO A and B series. Nominal millimetre dimensions are used; rounded inch values do not redefine the sheet.
- NIST: SI units of length: the exact conversion of one inch to 25.4 millimetres. Inch and point values below are calculated from the stated nominal dimensions.
- Adobe Acrobat: adjust page size for printing: Actual Size, Fit and the difference between the page and the printable area.