When asking, for example, how long is the bridge.
Intuitively I'd say, Quanto lungo è il ponte. However, the correct translation seems to be Quanto è lungo il ponte.
Why is it Quanto è lungo ... instead of Quanto lungo è ...?
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As a Central Italian, I find any construction of the form quanto + adjective + verb essere to be very strange-sounding, both in interrogative and exclamative sentences. I trust other commenters who find them utterable, and even so in limited contexts, but I'd attribute it more to regional differences than to colloquial or emphatic registers.
To source this, lest it remain an I-say-so thing, apparently neither Treccani dictionary nor the Grande dizionario della lingua italiana (we are interested here in Quanto2, starting at the end of p. 63), nor De Mauro's dictionary, nor Zingarelli (behind a paywall) seem to record anything of the form “quanto + adjective + verb essere”.
My temporary conclusion (which I'll be ready to change if new evidence appears) is that that form is acceptable – in suitable contexts – in some Northern varieties of Italian, but not in Standard Italian.
In a (very) broad sense, the order of phrase elements in Italian is quite free, sometimes leading to slightly strange utterances, up to never heard ones, but still understandable. Undoubtedly there is a standard and clean order, more used in "controlled" text found in books or, generally, written text.
But when coming to spoken phrases, especially in dialogs, things can change a lot: elements can be dropped, leaving them implicit, and the order can be changed to put emphasis somewhere, normally the first word. Lastly, redundancy sometimes happens, like the famous "a me mi piace". The mechanism for this last sentence can be the following: a speaker is asked about what it likes, and the first concept that arises in its mind is "a me", because the speaker is replying, speaking about itself; but, after that, the very common phrase "mi piace" should be changed to simply "piace", but perhaps is too late, and "a me mi piace" comes out.
About "Quanto è lungo", in a spoken dialog the phrase can turn to "Quanto lungo è" because the listener, not satisfied, wants to now "how much long" ("quanto lungo") at first. The dialog can be:
Mario: "Questo ponte è molto lungo"
Luigi: "Quanto?" (neutral)
...or "Sì, ma quanto?" (concessive)
...or "Sì, ma quanto lungo?" (impatient)
...or "Sì, ma quanto lungo è?" (even more impatient)
** UPDATE ** A comment says that in the above phrases the subject is implicit, and this would change the situation. Let's see how it would sound with an explicit subject:
"Sì, ma quanto lungo è questo ponte?"
...or "Sì, ma quanto lungo è questo benedetto ponte?!" (substitute benedetto with something more appropriate, and write the whole phrase in capital letters)
"E quanto lungo sarebbe questo ponte?" (sceptic)
which would sound the same as if it was:
"E quanto sarebbe lungo questo ponte?"
I think that the subject, implicit or not, does not matter.
In this dialog, the phrase "Quanto è lungo?" would not transmit the sense of impatience. In live dialogs, stresses on words can help, but even without stresses and/or prosody the above phrases are clearly impatient, at least to me.
The following two searches by Ngram Viewer show how common are the "standard" constructions versus the "colloquial" ones:
"quanto è lungo" is about 10-20 times more common.
"quanto è grande" is only about 3 times more common.