Binding of Isaac: Rebirth Wiki

Number One is a passive item.



  • Number One doesn't increase the tear rate cap, meaning picking it up with tears capped (normally 5.0) this item will just decrease range with no benefit.


  • Brimstone Brimstone / Added in Repentance Tainted Azazel Tainted Azazel: The laser turns yellow and charges at a much faster rate with no decrease to the range.
  • Epic Fetus Epic Fetus: Increases fire-rate with no decrease in range. Explosive clouds are now yellow.
  • Added in AfterbirthIncubus Incubus: The Incubus fires at a much faster rate with no decrease to the range.
  • Ipecac Ipecac: Increase fire rate moderately and decreases range only slightly.
  • The Ludovico Technique The Ludovico Technique: Turns tear yellow and allows it to be moved much faster.
  • Number One Number One: Gives an additional fire rate bonus without further reducing range.
  • Added in Afterbirth †Pop! Pop!: Eyeball tears are yellow, can be fired much quicker, and does not affect their airtime.
  • Technology Technology: The laser turns yellow and Technology's firing rate is greatly increased with no decrease to the range.
  • Added in AfterbirthTech X Tech X: Laser turns yellow, charge time is greatly decreased, and no decrease to the range.
  • Tiny Planet Tiny Planet: Tears travel roughly the same distance but can be fired much quicker.


  • Azazel Azazel: Lowers range, reduces charge time.
  • Added in Afterbirth †Compound Fracture Compound Fracture / The Parasite The Parasite: Tears often disappear before being able to split. Split tears also only travel a very short distance.
  • Cricket's Body Cricket's Body: Tears disappear very quickly after being fired and split tears barely travel at all.
  • Dr. Fetus Dr. Fetus: Not recommended. Makes bombs travel distance very short. The extremely reduced range can turn simple rooms into a challenge and self-damage a constant concern.
  • Added in Afterbirth †Haemolacria Haemolacria: Does not affect the main tear; however, burst tears travel significantly less far.
  • Added in AfterbirthKidney Stone Kidney Stone: Number One's range penalty overrides Kidney Stone's. The stone is not affected by short range, otherwise the combo behaves as expected.
  • A Lump of Coal A Lump of Coal: Tears still increase in size and damage as they travel; however, the short-ranged distance limits tear size and damage.
  • Added in AfterbirthMarked Marked: Tears become orange. The firing rate is increased, Marked's effect is unaffected but the range is reduced.
  • Mom's Knife Mom's Knife: The knife turns yellow and the maximum range is significantly reduced.
  • Removed in Repentance Monstro's Lung Monstro's Lung / Added in Afterbirth †Lead Pencil Lead Pencil: Not recommended. Tear barrage disappears very close to Isaac.
    • Added in Repentance Range is more forgiving.
  • Removed in RepentanceProptosis Proptosis: Not recommended. Tears disappear after traveling a very short distance.
    • Added in Repentance This is now fixed and works as expected.
  • Rubber Cement Rubber Cement: Tears often disappear before being able to bounce off walls.
  • Toothpicks Toothpicks: Tears become orange.

In-game footage[]


  • "Number One" is a euphemism for urination and mirrors "Number Two" being an euphemism for defecation.
    • This is why the tears fired after collecting this item are no longer fired from the head, but the lower waist.
  • In the original Binding of Isaac, Number One had the effect of turning all future Range Down pills into Range Up pills. This was presumably designed to reduce the risk of players being stuck in situations where their range would become too low to clear certain rooms. However, in Rebirth, Number One no longer has this effect, and will not turn Range Down pills into Range Up pills.
  • This item is used in High Brow (challenge #2).
  • Removed in Afterbirth † The firing animation of Number One is a little different from what it looks like in the original Binding of Isaac.


PC J172 PRAK (Treasure Room adjacent to spawn)

PC VMA3 SMZA (Treasure Room adjacent to spawn)

PC Added in Afterbirth Hard mode only SRX8 FXHM (Treasure Room adjacent to spawn) (XL floor)

3DS 0RJ7 VQYY (First floor Treasure Room)

PS4 WYH4 A4DX (First floor Treasure Room)