ISO 216 format with a 1:√2 ratio
Print preparation guide
A4 vs US Letter for Printing and Layout
Compare A4 and US Letter in millimetres, inches, pixels and aspect ratio, then adapt a full-page layout without accidental crop or reflow.
Quick answer
A4 is 210 × 297 mm; US Letter is 8.5 × 11 inches, or 215.9 × 279.4 mm. In portrait, Letter is 5.9 mm wider and 17.6 mm shorter. At 300 PPI, A4 rounds to 2480 × 3508 px while Letter is exactly 2550 × 3300 px.
fit scale = smaller of target width ratio and target height ratio215.9 × 279.4 mm with a 17:22 ratio
Letter is wider and shorter in portrait
Decision table
A4 and US Letter at common print resolutions
| Format | Physical trim | Pixels at 300 PPI | Layout effect |
|---|---|---|---|
| A4 | 210 × 297 mm | 2480 × 3508 | Taller, slightly narrower page |
| US Letter | 8.5 × 11 in | 2550 × 3300 | Wider, noticeably shorter page |
| A4 fitted on Letter | Scale to about 94.1% | Depends on source | Side margins remain |
| Letter fitted on A4 | Scale to about 97.3% | Depends on source | Top and bottom margins remain |
The formats are close, but not interchangeable
A4 belongs to the ISO A-series and measures 210 × 297 mm. US Letter measures 8.5 × 11 inches, exactly 215.9 × 279.4 mm. Letter gains 5.9 mm across the short edge but loses 17.6 mm along the long edge.
That difference is enough to change page breaks, move a footer, crop a full-bleed background or leave uneven borders. Selecting Letter in a print dialog does not automatically redesign an A4 document.
Their aspect ratios explain the crop
A4 has the ISO 1:√2 proportion, approximately 0.707 in portrait width-to-height terms. Letter is 17:22, approximately 0.773. Letter therefore appears wider relative to its height.
Filling one format with artwork designed for the other requires a crop. Fitting preserves the complete page but leaves margin space. Stretching changes shapes, typography and logos and is normally the least defensible choice.
Pixel dimensions depend on PPI
At 300 PPI, A4 rounds to 2480 × 3508 px because its metric dimensions convert to non-integer inches. Letter is exactly 2550 × 3300 px because its physical definition is already in inches. At 150 PPI, the corresponding values are 1240 × 1754 px and 1275 × 1650 px.
Those are trim dimensions. Add the provider's bleed after choosing the format: an A4 canvas with 3 mm bleed is 216 × 303 mm, while Letter with 0.125 inch bleed becomes 8.75 × 11.25 inches.
Adapt documents by reflowing or fitting intentionally
For editable documents, change the page size, inspect every page break, reposition full-page elements and verify headers, footers and tables. This preserves readable type and uses the new page area deliberately.
For a fixed PDF or image, choose fit when every element must remain visible, or crop only after previewing the exact lost area. A4 fitted within Letter is limited by Letter's shorter height and scales to roughly 94.1%, leaving side margins. Results can vary with printer non-printable margins.
Choose the format for the audience and printer
A4 is the normal office and publication format in most countries using the ISO system. US Letter is common for North American office documents, forms and home printers. The correct choice is the format the recipient and production service actually expect.
When one file must serve both audiences, design with generous internal margins and avoid placing critical elements close to any edge. Export and inspect both versions rather than relying on a viewer's automatic shrink-to-fit setting.
Practical workflow
Use this order before you export.
- Identify the recipient's required paper format.
- Change the editable page size or choose fit for a fixed file.
- Inspect page breaks, edge elements, borders and full-bleed artwork.
- Recalculate pixels and bleed for the selected final format before export.
Sources and method
Check the requirement behind the number.
These guides explain repeatable calculations and planning ranges. The print provider's written specification remains the final production requirement.
Put the guide into practice
Compare paper pixel sizes →Letter is wider and shorter than A4, so a full-page design should be reflowed or fitted—not silently stretched.
Use the linked calculator with your own dimensions, then verify the result against the provider's production requirement.