Can my UK PhD permit me to use the title "Dr.-Ing." in Germany?
One important thing you need to know about the German Doktorgrad is (alongside other non-academic titles) that its use is restricted by federal law. Adding a Doktortitel to your name in public without being entitled to do so is a punishable offence. This means that you should not trust any answer that you get from the Internet on this topic. Make sure that you verify whatever answer you get with an official side. One way of doing so is pointed out in @Cachapa's useful answer from the point of view of someone who already went through this.
Having said that: First of all, a British Doctor of Philosophy is indeed considered equivalent to a German Doktorgrad. You can verify that using this database (unfortunately only available in German). This means that you're fully qualified for whatever position or task that requires a Dr.
However, while you're entitled to use your PhD in public as an academic title, it is not possible to convert your PhD into a German Doktorgrad, and doing so might be an offense according to German law. This is based on a statement issued by the Kultusministerkonferenz (the "Standing Conference of the Ministers of Education and Cultural Affairs of the Länder in the Federal Republic of Germany"). These are the crucial points:
- Akademische Grade sind in Deutschland rechtlich geschützt.
- Der ausländische Grad muss ordnungsgemäß verliehen sein.
- Die Umwandlung eines ausländischen Grades in einen deutschen Grad ist nicht möglich (…).
My translation:
- Academic titles are protected by the law in Germany.
- A foreign title has to have been granted lawfully.
- It is not possible to convert a foreign title into a German title.
This statement is very explicit in my opinion, and it means that you cannot just add Dr.-Ing. to your name if you haven't been granted the title by a German university. It also means that no German university can grant you a Dr.-Ing. simply because you have a foreign equivalent title.
Yet, you can use your PhD in public, because it's acknowledged as an academic title. Plus, the Kultusministerkonferenz has decided that EU members can also choose to use Dr. instead of the designation used in their country of origin, this is regulated in (2) in the "Vereinbarung über begünstigende Regelungen der 'Grundsätze für die Regelung der Führung ausländischer Hochschulgrade'" (thanks to @Pont for pointing that out), but this does not include the "-Ing." part. To quote:
- Hochschulgrade aus Mitgliedstaaten der Europäischen Union (EU) oder des Europäischen Wirtschaftsraumes (EWR) […] können in der Originalform ohne Herkunftsbezeichnung geführt werden.
This means that academic titles from the EU, the EEA may be used as part of the name in their original form without stating their origin.
- Inhaber von in einem wissenschaftlichen Promotionsverfahren erworbenen Doktorgraden, die in den in Ziff. 1 bezeichneten Staaten oder Institutionen erworben wurden, können anstelle der im Herkunftsland zugelassenen oder nachweislich allgemein üblichen Abkürzung […] wahlweise die Abkürzung „Dr.“ ohne fachlichen Zusatz und ohne Herkunftsbezeichnung führen. […] Führung beider Abkürzungen ist nicht zulässig.
This means that a holder of a doctorate from one of the countries described in (1) may decide to use the abbreviation Dr. instead of the abbreviation that is usually used in their country of origin, but without the addition of an abbreviation indicating the title-granting discipline – that's the part referring to the -Ing. suffix. Also, it's not possible to combine both abbreviations, i.e. "Dr. Schmuddi, PhD" is not allowed.
Of course the UK has decided to leave the EU, and as it is, it's not clear yet how this will affect this regulation. In the current form of the "Vereinbarung", that regulation will not apply automatically to UK PhD holders any more. I am so very much not a lawyer, but in my understanding, a PhD from the UK will not be entitled to use Dr. any more once the UK has left the EU, unless the Kultusministerkonferenz revises the "Vereinbarung". I'm pretty sure that they will do that very soon by adding the UK to the list of countries in (4) (alongside Australia, Israel, Japan, Canada, and the US). Yet, you never know.
Schmuddi already gave a very complete answer above, but I can add my personal experience since I am in the exact same situation: I completed my PhD in Engineering at a British university and am currently residing in Germany.
When you arrive in Germany you will have to do your Anmeldung - register yourself with your city's local authority. You can officially declare your PhD/Dr. title in that process and it will appear in the document you will get from them. I feel that's the safest way to use the title since it's been accepted by the state. As stated above, Germans take their titles very seriously and you do not want to use it incorrectly.
In order to register the title officially you'll need to bring proof of enrolment and completion of the PhD program. In my case I had to ask for a letter from my university with my full name and birthdate confirming my enrolment. For proof of completion I simply brought my diploma. Both documents were in English and were accepted without issue.
Finally, I prefer to sign as "Dr." rather than "PhD" since most Germans aren't familiar with the latter and even many of those who heard of it think they're not equivalent. I've also had a lot of people ask me if I studied Philosophy - consider this if you decide to hang your diploma where others can see it.
I would have commented to @Cachapa's answer, but I don't have the reputation...
I'd like to relate my story: I attempted to claim the Dr. title from Finland in the local Einwohnermeldeamt. I was asked for a German translation of the diploma that was already written in English. This probably depends on the state you are in, if not even on the language skills of the officials. In any case, having the diploma translated by a certified translator would have been ridiculously expensive, so I gave up. Therefore I do not dare to include the title at the moment. Perhaps I'll try the Amt again later.
Here are some relevant pieces of information I found:
"Foreign Academic Degrees Questions regarding the use of foreign academic degrees and titles should be addressed to the ministry of science of the respective Land. As a rule, it is possible to use the academic degree or title in the original language – this is also stipulated in the Länder higher education laws. It is not possible to convert a foreign academic degree or title into a German academic degree or title. The only exception is in the case of ethnic German resettlers. The anabin database provides further information on the recognition of foreign higher education qualifications. " [1]
There is actually a whole database, called "ANABIN", of degrees that are already recognised. [2]
[1] https://www.anerkennung-in-deutschland.de/html/en/academic_recognition.php
[2] http://anabin.kmk.org/no_cache/filter/institutionen.html