Short answer
The shortest durood is "sallallahu 'alayhi wa sallam" (Allah bless him and grant him peace), or "Allahumma salli 'ala Muhammad". Either fulfils salawat. Writing only "SAW", "PBUH" or "S" is not a durood in itself; scholars disliked abbreviating it and advised writing it in full or using the sign ﷺ while saying it.
Any wording that asks Allah to bless the Prophet ﷺ fulfils salawat. Abbreviating it in writing, such as "SAW" or "صلعم", is makruh according to the scholars of hadith and fiqh; you should write it in full or say it as you write.
The four schools agree on this.
Explanation
Short forms of durood:
- sallallahu 'alayhi wa sallam: the most common short form, said after his name.
- Allahumma salli 'ala Muhammad: O Allah, bless Muhammad.
- Allahumma salli 'ala Muhammad wa 'ala ali Muhammad: adding his family.
- 'alayhis salatu was salam: upon him be blessings and peace.
Each of these is a complete salawat. The full and best form is Durood Ibrahim. The Prophet ﷺ said that whoever sends one salawat on him, Allah sends ten on that person, so even the shortest one has great reward.
What about SAW, PBUH and the ﷺ sign? Abbreviations like SAW, PBUH or the old Arabic صلعم are not a prayer; they are a label. Scholars of hadith such as Ibn al-Salah and al-Nawawi disliked them and asked writers to write the salawat fully. The sign ﷺ is a single character that spells out the full Arabic words, so many scholars see it as better than an abbreviation, especially if you say the salawat as you write. AmalKit uses ﷺ for this reason.
When it is wajib to say it. The Prophet ﷺ called the one who hears his name and does not send salawat "the miser". In the Hanafi school it is fard once in a lifetime; when his name is mentioned, the position many muftis give is that it is wajib once in a sitting and mustahabb each further time. See do you have to send salawat when you hear his name.
Short forms are perfect for daily dhikr: a hundred times a day takes only a few minutes. Try the tasbih counter and see durood on Friday.
The evidence
Quran, Surah Al-Ahzaab 33:56
إِنَّ ٱللَّهَ وَمَلَٰٓئِكَتَهُۥ يُصَلُّونَ عَلَى ٱلنَّبِىِّ ۚ يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ صَلُّوا۟ عَلَيْهِ وَسَلِّمُوا۟ تَسْلِيمًا ﴿٥٦﴾
Indeed, Allah confers blessing upon the Prophet, and His angels [ask Him to do so]. O you who have believed, ask [Allah to confer] blessing upon him and ask [Allah to grant him] peace.
The command behind every form of salawat.
Sahih Muslim 408
Sahih... من صلى علي واحدة صلى الله عليه عشرا ...
"Whoever sends one salah on me, Allah sends ten on him."
Even one short durood is greatly rewarded.
Jami' at-Tirmidhi 3546
Graded sahih... البخيل الذي من ذكرت عنده فلم يصل علي ...
"The miser is the one in whose presence I am mentioned and he does not send salawat on me."
Salawat is due when his name is mentioned.
Where the ruling is recorded
- Muqaddimat Ibn al-Salah, Section on writing hadith, on writing the salawat in full. Dislikes abbreviating the salawat in writing.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, discussion of salawat on the Prophet. The Hanafi ruling that salawat is wajib once in a sitting when his name is mentioned.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.