A4
A4
210 × 297 mm
Letter
US Letter
215.9 × 279.4 mm
Illustrations use a common visual scale for comparison; displayed outlines are not intended as a physical ruler.
Paper dimensions · Printing reference
A4 vs US Letter: compare paper sizes with confidence
Compare standard paper dimensions, convert measurements between millimeters, centimeters and inches, and choose a page format that fits your document and printer.
01 / Quick comparison
A4 and US Letter at a glance
These formats are close in size, but they are not interchangeable in every layout. A4 is narrower and taller; US Letter is wider and shorter.
Exact dimensions
| Format | Millimeters | Centimeters | Inches |
|---|---|---|---|
| A4 | 210 × 297 | 21 × 29.7 | 8.27 × 11.69 |
| US Letter | 215.9 × 279.4 | 21.59 × 27.94 | 8.5 × 11 |
A4 is 5.9 mm narrower and 17.6 mm taller than Letter. Its area is about 3.4% larger, but area alone does not determine which layout will print better.
Practical rule: choose the page size requested by the recipient, form, institution, or local office. If none is specified, use the default commonly expected by your audience and printer.
02 / Interactive tool
Paper size converter
Select a standard format and display its width and height in your preferred unit. Measurements are shown in portrait orientation.
The converter runs locally in your browser; no measurements are sent to a server.
210 × 297 mm
A4 paper · width × height · portrait orientation
Reference dimensions
| Format | Width × height (mm) | Width × height (cm) | Width × height (in) | Common context |
|---|---|---|---|---|
| A3 | 297 × 420 | 29.7 × 42.0 | 11.69 × 16.54 | Large diagrams, posters, plans |
| A4 | 210 × 297 | 21.0 × 29.7 | 8.27 × 11.69 | Letters, reports, school work |
| A5 | 148 × 210 | 14.8 × 21.0 | 5.83 × 8.27 | Booklets, small notes, flyers |
| US Letter | 215.9 × 279.4 | 21.59 × 27.94 | 8.5 × 11 | Common office documents in the US |
| US Legal | 215.9 × 355.6 | 21.59 × 35.56 | 8.5 × 14 | Forms and documents needing extra length |
Inch conversions for ISO sizes are rounded to two decimal places. US Letter and Legal are defined in inches; their millimeter equivalents are exact conversions using 25.4 mm per inch.
03 / Visual guide
How the common formats compare
Paper labels can look similar on screen. The measurements and proportions below help clarify the differences; the outlines are schematic, not a print calibration tool.
A-series sizes
A5
A5
148 × 210 mm
A4
A4
210 × 297 mm
A3
A3
297 × 420 mm
Each next A-series size has half the area of the previous size, rounded to its specified whole-millimeter dimensions.
Letter and Legal
Letter
US Letter
8.5 × 11 in
Legal
US Legal
8.5 × 14 in
Legal paper keeps the same width as Letter but adds 3 inches (76.2 mm) of length.
04 / Practical printing
Choose the right size in your document and print dialog
Paper size is only one part of a successful print. The document page, printer setting, paper loaded in the tray, and scaling option should agree whenever possible.
1. Set the page size before formatting
In a word processor or page-layout app, look for a command such as Layout, Page setup, or Document settings, then select A4, Letter, Legal, or the required format. Menu names vary by application and version. Set the size before fine-tuning tables, headers, footers, and page breaks; changing it late can reflow the document.
2. Check the print dialog
- Open the document's print command.
- Choose the intended printer and open its paper or page-size settings.
- Select the same size used by the document, if the printer supports it.
- Check orientation, page range, duplex settings, and tray selection.
- Preview the pages before printing, especially forms, tables, and documents with page numbers near the edge.
3. Understand “fit,” “actual size,” and cropping
Fit to page scales the content to fit within the selected sheet. This can prevent clipping, but it may shrink text or diagrams. Actual size or 100% printing preserves the document's specified physical scale; content outside the printer's printable area can be clipped. Options such as “fill page” may enlarge content and crop edges. The exact labels differ between apps and printer drivers.
A4 is taller and narrower than Letter. When an A4 document is printed on Letter, the extra height can be cut off at 100% scale; fitting it may reduce the content slightly. A Letter document printed on A4 may leave more vertical space or be scaled, depending on settings. Always inspect the preview rather than assuming the printer will make the layout match automatically.
4. Leave room for printer margins
Many home and office printers cannot print to the very edge of ordinary paper. Keep important text, page numbers, and logos inside a safe margin appropriate for the printer. A common starting point for ordinary office documents is around 10–15 mm, but the device's non-printable area and the document's requirements take precedence. Borderless printing, when available, is a separate feature and may enlarge or crop the image slightly.
For professional print production, distinguish the page trim size from bleed and safe area. Bleed is artwork that extends beyond the trim edge so small cutting variations do not leave an unprinted sliver; the required amount depends on the printer or print shop. Do not assume that a desktop printer can reproduce full-bleed artwork.
5. When to use each format
- A4: a sensible default for general documents in many countries using ISO paper sizes, including reports, letters, worksheets, and forms designed for A4.
- US Letter: commonly expected for everyday office documents in the United States and some nearby markets. Use it when a form or recipient specifies Letter.
- US Legal: useful when a template or workflow specifically calls for the longer 8.5 × 14 inch sheet. Do not select it merely because a document is legal in subject matter.
- A3: offers roughly twice the area of A4 and can help with large charts, spreadsheets, and diagrams, provided the printer supports it.
- A5: half the area of A4 in the ISO A-series system; useful for compact booklets, handouts, and smaller-format documents.
Before printing an important document: confirm the requested format, check the page preview, verify the loaded paper, and print one test page if layout errors would be costly.
05 / Standards and FAQs
How paper size standards work
The ISO A-series
The ISO 216 A-series defines trimmed paper sizes used for writing and certain printed materials. A0 is 841 × 1189 mm, with an area close to one square metre. Each next size is made by halving the preceding sheet parallel to its shorter side, yielding the familiar sequence A0, A1, A2, A3, A4, A5 and onward. Small rounding differences are part of the specified whole-millimeter sizes.
The A-series has a distinctive aspect ratio of approximately 1:√2. That proportion means a sheet can be halved and retain the same shape, which makes scaling and folding between adjacent sizes convenient. For example, two A5 sheets fit into A4 by area, and two A4 sheets fit into A3.
International and North American formats
A4 belongs to the ISO 216 system. US Letter and US Legal are common North American formats with dimensions conventionally expressed in inches. These systems evolved separately, so there is no exact one-to-one equivalent for every size. Letter is close to A4, but the width and height differ enough to affect page breaks, form alignment, and scaled graphics.
Regional defaults are useful clues, not guarantees. A global organization may use A4 in one office and Letter in another; a government form, school, publisher, or printer specification can override local convention. Use the format stated in the instructions whenever there is one.
Measurement and rounding
One inch is exactly 25.4 millimeters. The converter calculates unit changes from standard dimensions and rounds the display for readability. As a result, a displayed inch value multiplied back into millimeters may differ by a small fraction due to rounding. For layout-critical work, keep the source unit and precision required by your document or print provider.
Frequently asked questions
What is A4 paper size in inches?
A4 measures 210 × 297 mm, which is approximately 8.27 × 11.69 inches.
Is A4 the same as US Letter?
No. A4 is 210 × 297 mm; US Letter is 8.5 × 11 inches (215.9 × 279.4 mm). Letter is wider and shorter.
Which is bigger, A4 or Letter?
A4 has slightly more total area and is taller, while Letter is wider. The difference in shape matters as much as the area when printing fixed layouts.
Can I print an A4 PDF on Letter paper?
Usually, if the printer supports Letter. Select the paper actually loaded and review the preview. “Fit to page” can reduce content to fit, while 100% scale can clip content near the edges.
What is US Legal paper size?
US Legal is 8.5 × 14 inches, or 215.9 × 355.6 mm. It is the same width as Letter but longer.
What is the difference between A3, A4, and A5?
A3 is 297 × 420 mm, A4 is 210 × 297 mm, and A5 is 148 × 210 mm. Each adjacent A-series size is approximately half or double the area of its neighbor.
Why does my printed document have white edges?
Most printers have a non-printable margin. Keep content within the printer's printable area, or use a supported borderless mode when the job requires edge-to-edge printing.
Does changing paper size change the document?
It can. Text may reflow, tables can move, and page breaks can change. Set the intended page size early and review the entire document after changing it.
Sources and further reading
Dimensions and standards background were cross-checked against the following references. This site is an independent educational reference and is not affiliated with these organizations.