A4 paper vs American letter size

No, nobody even will notice. As long as the QR or Bar code is printed clearly, 8 1/2 by 11 is fine.

"A4" in that context is really just shorthand for letter-size paper, which (of course) U.S. letter-size paper is. They just don't want someone trying to use A5 or A6 (much smaller) formats. The slight difference in dimensions between A4 and U.S. letter paper are unimportant for this purpose.

Thank you. Besides downloading to my phone I want a backup printed on paper.

To be absolutely safe, print it out as is and not sized to the paper.

This used to be important, although most bar code readers seem to cope perfectly well this days with scaling.

US letter size if 8.5 by 11". A4 is roughly 8.25 by 11.69" Slightly narrower and slightly longer. It will print just fine on US paper.

The first time I home-printed a German Rail Sparpreis ticket (then called a Dauer-Spezial ticket) I was worried about the A4 paper vs out 8½x11 paper, so I took 8½x14 paper and cut it down to A4 size and printed the ticket on it (I could select A4 on my printer). Then I selected 8½x11 and printed it again. Not much different; not exactly the same size or proportion, but close. I took both printouts with me, rolled up in a cardboard tube so they wouldn't get folded. I also took along the .pdf file on a thumb-drive and had the host at my first accommodation print it on his paper. Again, close to my "A4" printout, but not exactly. I forget which one I actually gave the conductor, but when I saw him position his "tricorder" about a foot (305 mm) from the paper and approximately perpendicular, I realized the size and proportion don't really matter.

A lot of Bahn ticket terminals used to print on A5 paper (similar to our "statement" size), which is the same width as A4 but half the height. I think they say A4 because they don't want the ticket printed on A5 paper.

There is a note next to the barcode that says, "Barcode bitte nicht knicken!" (Please don't "kink" the barcode).

Since that trip, three more tickets, I have just printed the ticket on 8½x11 paper, and it has always worked fine. I've even folded the ticket top to bottom across the horizontal mid-line, and it works. Just don't fold it across the barcode.

"A4" in that context is really just shorthand for letter-size paper, which (of course) U.S. letter-size paper is.

No, A4 means A4. A standard metric size paper. It would be a waste of space to add a special exception for the one country in the World that does not use the metric system.
But, yes +/- 10% (or 20%) won't make any difference, so long as the writing is clear and the barcode/QR code can be read by the machine. They just don't want you to shrink it to 50%.

P.S. When will the US finally join the rest of the world and adopt the metric system, and consign inches, miles, pounds and °F to the dustbin of history?

I was taught about the metric system fairly early during my school years--late 1950s or early 1960s. At that time, we expected to convert. It never happened. I still think in inches/feet/miles, ounces/pounds, pints/quarts/gallons, but at least I can convert mentally if I need to.

It is insane that we haven’t converted to the metric system. I too learned it in school in the 60s with the expectation that we would soon be converting. Yeah it would take some time to get used to thinking in metric, but so what. It would be so much easier. I still can’t remember how many yards are in a mile or how many pounds are in a ton!

I also can’t stand that we don’t use the 24 hour clock. It is such a pain having to use am and pm.

And while I am on a roll... i think it makes more sense to put the date before the month. : )

Why do they even use a 24 hour clock in the metric system, or 60 sec/min, or 60 min/hr? Or why is the weight of 1 kg = 9.81 Newtons?

Aren't all conversions supposed to be in powers of 10? Or, for that matter, why do we even use a base 10 numbering system (hint: how many fingers do you have?). A base 8 or base 16 system would make more sense since it would convert directly to binary, the system used by computers.

By the way, I agree with European date convention and with using a 24 hour clock (or at least one that uses the complete number of time periods per day. I have the clocks on my computer and phone set to 24. But I've never seen a analog clock with a 24 hr face.

And wasn't Chris's post a violation of Community Guideline #1, "Stay on topic".

Lee, if my post was off topic (only the last sentence), yours was more so ☺. I see it as informing travellers of useful background information.

I think the French tried a decimal clock and a decimal calendar, but it soon got dropped. See here: https://en.wikipedia.org/wiki/French_Republican_Calendar

Base 12 would be the best system, as 12 has lots of factors. The old "LSD" money in the UK used to be base 12:
1 Shilling (1/-) = 12 pence (12d), £1 = 20 shillings = 240d, but they abolished that to make it "decimal": £1 = 100p
Changing to base 12 would involve inventing 2 new number symbols (for ten and eleven), and changing the whole of arithmetic, too much.

1 Kg is a measure of mass, which stays unchanged, Newtons are a measure of weight (or force). 1 Kg only = 9.81 Newtons on the earth's surface, because gravity = 9.81 m/s², on the moon it would be a different value.

Reminds me of the time I was with some US-Americans walking through the city, and there was a big indicator display on the side of a building, alternating between displaying:
16:11, 21 02 and +5°
They asked me what it meant. I was a bit confused, obviously time, date and temperature. Then I realised that in the US they use different systems for all 3!

You can special order A4 paper from Staples

I’ve printed both of those on 8.5 x 11” paper and no issues using them at those locations. Enjoy your trip to Paris!

P.S. When will the US finally join the rest of the world and adopt the metric system, and consign inches, miles, pounds and °F to the dustbin of history?

Probably when Britain, Japan, et. al., convert to driving on the right side of the road.

And I will leave you all with this ----
God grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.

No, A4 means A4. A standard metric size paper.

Of course it means A4. And A4 is, as I've stated, shorthand (which is a perhaps somewhat archaic piece of American slang essentially meaning an abbreviation or a shortened way of referring to something) for letter-sized paper such as the type commonly used in business.

Bob, A4 is not "shorthand" for US letter size. They are two different sizes. You could perhaps say A4 is approximately the same size as US letter.
A4 is 210 mm × 297 mm (1/16 m²). US letter (8½ × 11 inches) is 216 mm × 279 mm
See diagram here: https://images.uk.onlinelabels.com/images/learning-center/A4-vs-US-Letter.png

I have had enough grief in the past with documents in US sizes not fitting on "normal" A4 paper to know they are not the same.

A small change in barcode size should not invalidate the barcode. Just make sure that the entire barcode is printed and not truncated.

https://internationalbarcodes.com/ean-13-specifications/

The specified magnification range for an EAN-13 Bar Code Symbol being
scanned at retail point of sale is 80% – 200% (X-dimension
0.26mm-0.66mm).

Bob, A4 is not "shorthand" for US letter size. They are two different
sizes. You could perhaps say A4 is approximately the same size as US
letter.

Chris F, I don't know if this is an English as a second language problem or what, but I did not write that "A4 is 'shorthand' for US letter size." I wrote that it's shorthand for letter size, meaning in Europe, and other places as well.

It's similar enough in size to US letter size (also referred to as eight-and-a-half-by-eleven, or 8-1/2 x 11, in reference to its size in inches) that the use proposed by the original poster should be fine.

I've worked in France for years on projects in both the U.S. and various places in Europe, and am well aware of the differences in business letter size paper between the two areas.

Countries in the world where ISO paper sizes are not the most widely used: Belize, Canada, Chile, Colombia, Costa Rica, El Salvador, Guatemala, Mexico, Nicaragua, Panama, Philippines, Puerto Rico, United States, Venezuela. Most, but not all of these use the USA paper sizes, or a close equivalent.

I can remember using the old British sizes of foolscap folio (8 × 13 inches), large post quarto (8 x 10) and small post quarto (7 x 9). Took about 15 years for them to fade away but they are long gone now outside of specialists and paper for handwriting letters.

Sam, you forgot "The west was won by the mile, not the 1.6 kilometer!"

waves hand - Canadian here - all the printer paper I buy is 8 1/2 by 11.

And even tho I was born in the 70's, I still need to know my weight in pounds and my height in feet. But I use km, litres and Celsius. And cm interchangeably with inches - when I print a photo - I know what 8x10 is, but if you told me that in cm, I'd look at you like you had two heads.

I recently replaced my old HP Inkjet printer with a newer HP OfficeJet 6900 Series printer. HP is smart enough to have the printer compatible with both common US paper sizes ("letter size") and metric size paper including A4 paper:
https://support.hp.com/us-en/product/hp-officejet-6960-all-in-one-printer-series/9514854/model/9514772/document/c05061732

Supported paper sizes

U.S. Letter: 216 x 279 mm (8.5 x 11 inches)

A4: 210 x 297 mm (8.3 x 11.7 inches)

Some of the sizes originate from Revolutionary France conceived alongside the development of the metric system, with which they were closely associated, although the current set of series are based on a German standard. A0 paper has an area of 1 square metre, (as mentioned in the reference Emma quotes which wasn't there when I started this reply!).