Battlefield 3 XP Points to Rank Up for each Class, see the chart below which will show you all the xp points needed to rank up to unlock weapons dog tag and much more. You may unlock a Specialization or Weapon too. You start out on rank 0, no real rank name, and basic weapons. The following list has the level, the rank name, the XP needed to rank up, and the total amount of XP needed.
Battlefield 3 XP Points to Rank Up for each Class
Private First Class: 500 (500) XP – 870 MCS
Private First Class 1 Star: 5,500 (6,000) XP – SPRNT
Private First Class 2 Stars: 6,000 (12,000) XP
Private First Class 3 Stars: 5,000 (17,000) XP – G17C
Lance Corporal: 6,000 (23,000) XP – AMMO
Lance Corporal 1 Star: 5,000 (28,000) XP
Lance Corporal 2 Stars: 6,000 (34,000) XP – PP-2000
Lance Corporal 3 Stars: 5,000 (39,000) XP – FLAK
Corporal: 6,000 (45,000) XP
Corporal 1 Star: 5,000 (50,000) XP – M9 Tactical
Corporal 2 Stars: 5,000 (55,000) XP – EXPL
Corporal 3 Stars: 11,000 (66,000) XP – MP443 Tactical
Sergeant: 14,000 (80,000) XP
Sergeant 1 Star: 10,000 (90,000) XP – COVR
Sergeant 2 Stars: 10,000 (100,000) XP
Sergeant 3 Stars: 20,000 (120,000) XP – UMP-45
Staff Sergeant: 10,000 (130,000) XP – SUPR
Staff Sergeant 1 Star: 20,000 (150,000) XP
Staff Sergeant 2 Stars: 20,000 (170,000) XP – G17C Silenced
Gunnery Sergeant: 10,000 (180,000) XP – FRAG
Gunnery Sergeant 1 Star: 20,000 (200,000) XP
Gunnery Sergeant 2 Star: 20,000 (220,000) XP – M1014
Master Sergeant: 20,000 (240,000) XP – SQD SPRNT
Master Sergeant 1 Star: 20,000 (260,000) XP
Master Sergeant 2 Stars: 30,000 (290,000) XP – M9 Silenced
First Sergeant: 20,000 (310,000) XP – SQD AMMO
First Sergeant 1 Star: 30,000 (330,000) XP
First Sergeant 2 Stars: 30,000 (360,000) XP – MP 443 Silenced
Master Gunnery Sergeant: 30,000 (390,000) XP – SQD FLAK
Master Gunnery Sergeant 1 Star: 20,000 (410,000) XP – G18 Silenced
Master Gunnery Sergeant 2 Stars: 30,000 (440,000) XP – SQD EXPL
Sergeant Major: 30,000 (470,000) XP – PDW-R
Sergeant Major 1 Star: 30,000 (500,000) XP – SQD SUPR
Sergeant Major 2 Star: 30,000 (530,000) XP – SAIGA 12K
Warrant Officer One: XP – SQD COVR
Chief Warrant Officer Two: XP – .44 MAGNUM
Chief Warrant Officer Three: XP – SQD FRAG
Chief Warrant Officer Four: (660,000) XP – DAO-12
Chief Warrant Officer Five: 40,000 (700,000) XP
Second Lieutenant: XP – P90
First Lieutenant: XP – G18
Captain: XP
Major: XP – USAS-12
Lt. Colonel: XP – .44 M-SCOPED
Colonel: XP – AS VAL, M412 REX, MP7, 93R