The Syrian Observatory for Human Rights has documented the death of 162,402 persons as of 18/03/2011, which witnessed the fall of the first martyr in Dera'a, and until 31/03/2014.
The casualties are as follows:
Civilians: 80,836 civilians including 8,607 children and 5,586 women
Rebel and islamic fighters: 26,858
Defected soldiers and officers: 2,314
Arab, European, Asian, American and Australian fighters from the ISIS, al-Nusra front, Junoud al-Sham battalion, Jund al-Aqsa battalion, Jund al-Sham movement and al-Khadra' battalion: 13,529
Regular soldiers and officers: 37,685
Combatants from popular defence committees, national defence forces, shabiha, pro-regime informers and the "Syrian resistance to liberate the Sanjak of Alexandretta": 23,485
Arab and Asian pro-regime militants: 1224
Fighters from Hezbollah : 438
Unidentified casualties (documented by pictures and footages): 2,891
It is worth noting that the numbers do not include more than 18,000 detainees in regime prisons and thousands of those who disappeared during regime raids and massacres. It also doesn't include more than 8,000 regular soldiers and pro-regime militants and hundreds of "regime supporters" captured by the ISIS, islam fighters, al-Nusra front and rebel fighters and hundreds of those kidnapped by pro-regime militants.
The numbers also do not include more than 1500 fighters from the YPG, ISIS, al-Nusra front, islamic battalions and rebel battalions who were kidnapped during clashes between the mentioned sides.