A4 is 8.27 × 11.69 inches (210 × 297 mm). US Letter is 8.5 × 11 inches (216 × 279 mm). A4 is 0.24 inches narrower and 0.69 inches taller — a difference that is invisible on screen and decisive in a frame.
The numbers side by side
| A4 | US Letter | |
|---|---|---|
| Width | 8.27 in / 210 mm | 8.5 in / 216 mm |
| Height | 11.69 in / 297 mm | 11 in / 279 mm |
| Aspect ratio | 1:1.414 | 1:1.294 |
| Area | 97.9 sq in | 93.5 sq in |
| Used in | UK, Ireland, EU, Australia, NZ, India, Singapore, Hong Kong, Malaysia, South Africa | United States, Canada (mostly), Philippines |
Two things follow from that table, and they cause most of the problems people run into:
- A4 is narrower, so it leaves a gap on the left and right in a letter-sized opening.
- A4 is taller, so it gets cropped at the top and bottom in a letter-sized opening.
Letter in an A4 opening has the opposite problem: it is too wide and too short, so it crops on the sides and floats vertically.
Why two standards exist
They are two unrelated systems. A4 is part of the ISO 216 series, where every size is derived by halving the previous one and the ratio stays at 1:√2. That is why A3 folds down to A4, and A4 to A5, without changing proportions.
US Letter comes from a different tradition and does not fold neatly into anything. It is part of the ANSI series, where the ratio is 1:1.294 — close enough to A4 to look the same on a desk, different enough to matter the moment you put it in a frame or a printer.
What it means for frames
This is where the difference costs money. Frame sizes are sold to the nearest standard: a "letter frame" has an 8.5 × 11 opening, an "A4 frame" has an 8.27 × 11.69 opening. Buy the wrong one and you have three options:
- Trim the document — never do this. It is irreversible, removes the border, and on a sealed document it can take part of the seal with it.
- Buy another frame — expensive, and you still have a spare frame.
- Use a custom mat — a mat cut to the document size, fitted inside a standard frame.
The third option is almost always the right one. A mat cut to the document size does two jobs: it covers the mismatch between document and opening, and it keeps the document off the glass. Two to three inches of mat around the document is the practical range.
The measurements for both formats, including mat widths, are in diploma frame sizes.
What it means for printing
If you are printing a document at home, the format mismatch shows up as one of two failures:
- Printing A4 onto letter paper. The page is too tall, so the bottom is cut off or the printer shrinks everything to fit.
- Printing letter onto A4 paper. The page is too wide, so it either crops on the sides or prints with an uneven margin.
Both are fixable, but only if you stop the print dialog from doing it automatically. Set scale to 100% and turn off "fit to page". A 3% shrink is invisible on screen and obvious against a frame opening.
The rest of the printing side — paper weight, printer settings, drying time — is covered in how to print a diploma at home.
What it means for covers and folders
Covers follow the same split. A letter-size cover holds an 8.5 × 11 document; an A4 cover holds an A4. Putting an A4 document into a letter cover works but the document shifts inside; putting a letter document into an A4 cover leaves it loose enough to slide.
Match the cover to the measured document, not to the word "standard".
How to tell which one you have
- Measure the width in inches. 8.5 means letter; 8.27 means A4.
- Measure the height. 11 means letter; 11.69 means A4.
- If neither matches exactly, you have a non-standard size — the formats that appear most often are listed separately.
Do not rely on the printed word. Plenty of documents say "A4" in the footer while being printed on letter stock, especially in institutions that changed stationery suppliers.
Common questions
Is A4 the same as 8.5 × 11?
No. A4 is 8.27 × 11.69 inches. It is slightly narrower and noticeably taller than letter.
Can I put an A4 certificate in a letter frame?
Only by cropping it or by using a mat that covers the gap. Cropping is permanent; a custom mat is not.
Which is bigger, A4 or letter?
Letter is slightly wider and slightly shorter. A4 has more area overall.
Do A4 frames exist?
Yes, but they are less common outside Europe. In the US you usually need a custom mat rather than a custom frame.
What about A3?
A3 is 11.69 × 16.54 inches — exactly two A4s side by side. Some European and Asian institutions use it for larger award certificates.
Everything sold on this site is a novelty reproduction for display, keepsake and prop use. It is not an official record and cannot be used to verify a qualification.
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Work out your own numbers: the diploma frame size calculator takes the width and height of your document and returns the frame opening and mat widths it needs, in inches or millimetres.